BLACKROCK MUNICIPAL BOND FUND, INC. (Form: 485BPOS, Received: 10/25/2019 12:38:39)

As filed with the Securities and Exchange Commission on October 25, 2019

Securities Act File No. 002-57354

Investment Company Act File No. 811-02688

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

☒

Pre-Effective Amendment No.

□

Post-Effective Amendment No. 66

☒

and/or

REGISTRATION STATEMENT UNDER THE

INVESTMENT COMPANY ACT OF 1940

☒

Amendment No. 64

☒

(Check appropriate box or boxes)

BLACKROCK MUNICIPAL BOND FUND, INC.

(Exact Name of Registrant as Specified in Charter)

100 Bellevue Parkway, Wilmington, Delaware 19809
United States of America

(Address of Principal Executive Offices)

Registrant’s Telephone Number, including Area Code: (800) 441-7762

John M. Perlowski

BLACKROCK MUNICIPAL BOND FUND, INC.
55 East 52nd Street

New York, New York 10055
United States of America

(Name and Address of Agent for Service)

Copies to:

Counsel for the Fund:
Margery K. Neale, Esq. Willkie Farr & Gallagher LLP 787 Seventh Avenue New York, New York 10019-6099	Janey Ahn, Esq. BlackRock Advisors, LLC 55 East 52nd Street New York, New York 10055

It is proposed that this filing will become effective (check appropriate box)

□ Immediately upon filing pursuant to paragraph (b)

☒ On October 28, 2019 pursuant to paragraph (b)

□ 60 days after filing pursuant to paragraph (a)(1)

□ On (date) pursuant to paragraph (a)(1)

□ 75 days after filing pursuant to paragraph (a)(2)

□ On (date) pursuant to paragraph (a)(2) of Rule 485

If appropriate, check the following box:

□ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.
Title of Securities Being Registered: Shares of beneficial interest, par value, $0.10 per share.

OCTOBER 28, 2019

Prospectus

BlackRock Municipal Bond Fund, Inc. | Investor and Institutional Shares

•	BlackRock High Yield Municipal Fund
	Investor A: MDYHX • Investor C: MCYHX • Institutional: MAYHX
•	BlackRock National Municipal Fund
	Investor A: MDNLX • Investor C: MFNLX • Institutional: MANLX
•	BlackRock Short-Term Municipal Fund
	Investor A: MELMX • Investor C: MFLMX • Institutional: MALMX

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of each Fund’s shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from BlackRock or from your financial intermediary, such as a broker-dealer or bank. Instead, the reports will be made available on a website, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

You may elect to receive all future reports in paper free of charge. If you hold accounts directly with BlackRock, you can call (800) 441-7762 to inform BlackRock that you wish to continue receiving paper copies of your shareholder reports. If you hold accounts through a financial intermediary, you can follow the instructions included with this disclosure, if applicable, or contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. Please note that not all financial intermediaries may offer this service. Your election to receive reports in paper will apply to all funds advised by BlackRock Advisors, LLC, BlackRock Fund Advisors or their affiliates, or all funds held with your financial intermediary, as applicable.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive electronic delivery of shareholder reports and other communications by: (i) accessing the BlackRock website at www.blackrock.com/edelivery and logging into your accounts, if you hold accounts directly with BlackRock, or (ii) contacting your financial intermediary, if you hold accounts through a financial intermediary. Please note that not all financial intermediaries may offer this service.

This Prospectus contains information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference.

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Prospectus. Any representation to the contrary is a criminal offense.

Not FDIC Insured • May Lose Value • No Bank Guarantee

Table of Contents

Fund Overview	Key facts and details about the Funds listed in this prospectus, including investment objectives, principal investment strategies, principal risk factors, fee and expense information and historical performance information
	Key Facts About BlackRock High Yield Municipal Fund	3
	Key Facts About BlackRock National Municipal Fund	10
	Key Facts About BlackRock Short-Term Municipal Fund	18

Details About the Funds	How Each Fund Invests	25
	Investment Risks	29

Account Information	Information about account services, sales charges and waivers, shareholder transactions, and distributions and other payments
	How to Choose the Share Class that Best Suits Your Needs	37
	Details About the Share Classes	41
	Distribution and Shareholder Servicing Payments	45
	How to Buy, Sell, Exchange and Transfer Shares	46
	Account Services and Privileges	52
	Funds’ Rights	53
	Participation in Fee-Based Programs	54
	Short-Term Trading Policy	54

Management of the Funds	Information about BlackRock and the Portfolio Managers
	BlackRock	56
	Portfolio Manager Information	58
	Conflicts of Interest	59
	Valuation of Fund Investments	59
	Dividends, Distributions and Taxes	60

Financial Highlights	Financial Performance of the Funds	62

General Information	Shareholder Documents	71
	Certain Fund Policies	71
	Statement of Additional Information	72

Glossary	Glossary of Investment Terms	73

Intermediary-Defined Sales Charge Waiver Policies

A-1

For More Information	Funds and Service Providers	Inside Back Cover
	Additional Information	Back Cover

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Fund Overview

Key Facts About BlackRock High Yield Municipal Fund

Investment Objective

The investment objective of BlackRock High Yield Municipal Fund (the “High Yield Fund” or the “Fund”) is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock and its affiliates) (each a “Financial Intermediary”) and in the “Details About the Share Classes” and the “Intermediary-Defined Sales Charge Waiver Policies” sections on pages 41 and A-1, respectively, of the Fund’s prospectus and in the “Purchase of Shares” section on page II-84 of Part II of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)		Investor A Shares		Investor C Shares		Institutional Shares
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)		4.25%		None		None
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)		None ¹		1.00% ²		None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)		Investor A Shares		Investor C Shares		Institutional Shares
Management Fee³		0.47%		0.47%		0.47%
Distribution and/or Service (12b-1) Fees		0.25%		1.00%		None
Other Expenses		0.26%		0.27%		0.24%
Interest Expense	0.16%		0.16%		0.16%
Miscellaneous Other Expenses	0.10%		0.11%		0.08%
Acquired Fund Fees and Expenses⁴		0.01%		0.01%		0.01%
Total Annual Fund Operating Expenses⁴		0.99%		1.75%		0.72%
Fee Waivers and/or Expense Reimbursements^3,5		(0.03)%		(0.04)%		(0.01)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^3,5		0.96%		1.71%		0.71%

¹	A contingent deferred sales charge (“CDSC”) of 1.00% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at the time of purchase as part of an investment of $250,000 or more.
²	There is no CDSC on Investor C Shares after one year.

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 56, BlackRock has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Municipal Bond Fund, Inc. (the “Corporation”) or by a vote of a majority of the outstanding voting securities of the Fund.

⁴	The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses.

⁵

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 56, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.79% (for Investor A Shares), 1.54% (for Investor C Shares) and 0.54% (for Institutional Shares) of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

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Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Investor A Shares	$519	$724	$946	$1,583
Investor C Shares	$274	$547	$945	$2,058
Institutional Shares	$ 73	$229	$400	$ 894

You would pay the following expenses if you did not redeem your shares:

	1 Year	3 Years	5 Years	10 Years
Investor C Shares	$174	$547	$945	$2,058

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Principal Investment Strategies of the Fund

Under normal circumstances, the High Yield Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The High Yield Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Although the Fund may invest in municipal bonds in any rating category, Fund management presently intends to invest at least 65% of the Fund’s net assets in medium- to low-quality bonds as rated by at least one independent rating agency (BBB or lower by S&P Global Ratings (“S&P”) or Fitch Ratings, Inc. (“Fitch”) or Baa or lower by Moody’s Investors Service, Inc. (“Moody’s”)), or if unrated, judged to be of comparable quality by BlackRock. Obligations rated below BBB or Baa are commonly known as “junk bonds.” It is possible that the Fund could invest up to 100% of its assets in “junk bonds.”

The Fund may also invest up to 10% of its assets in municipal bonds that are distressed securities. Distressed securities are securities that are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest at the time of acquisition or are rated in the lowest rating categories by at least one independent rating agency (CC or lower by S&P or Fitch or Ca or lower by Moody’s), or if unrated, judged to be of comparable quality by BlackRock. The Fund will usually invest in municipal bonds that have a maturity of five years or longer.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund. The order of the risk factors does not indicate the significance of any particular risk factor.

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■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
■	Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

■

Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or

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other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

■

Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.

■

Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the S&P^® Municipal Bond Index and the Custom High Yield Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

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Institutional Shares

ANNUAL TOTAL RETURNS

BlackRock High Yield Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 16.53% (quarter ended September 30, 2009) and the lowest return for a quarter was -6.25% (quarter ended June 30, 2013). The year-to-date return as of September 30, 2019 was 9.02%.

As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock High Yield Municipal Fund — Institutional Shares
Return Before Taxes	2.15%	6.95%	9.35%
Return After Taxes on Distributions	2.15%	6.94%	9.34%
Return After Taxes on Distributions and Sale of Fund Shares	2.96%	6.46%	8.73%
BlackRock High Yield Municipal Fund — Investor A Shares
Return Before Taxes	(2.35)%	5.76%	8.59%
BlackRock High Yield Municipal Fund — Investor C Shares
Return Before Taxes	0.14%	5.88%	8.24%
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
Custom High Yield Index¹ (Reflects no deduction for fees, expenses or taxes)	4.64%	7.21%	9.65%

The Custom High Yield Index reflects the returns of the S&P^® Customized High Yield Municipal Bond Index for periods prior to January 1, 2013, and the returns of only those bonds in the S&P^® Customized High Yield Municipal Bond Index that have maturities greater than 5 years for periods subsequent to January 1, 2013.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Shares only, and the after-tax returns for Investor A and Investor C Shares will vary.

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Walter O’Connor, CFA	2006	Managing Director of BlackRock, Inc.
Theodore R. Jaeckel, CFA	2006	Managing Director of BlackRock, Inc.

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Purchase and Sale of Fund Shares

You may purchase or redeem shares of the Fund each day the New York Stock Exchange is open. To purchase or sell shares, you should contact your Financial Intermediary, or, if you hold your shares through the Fund, you should contact the Fund by phone at (800) 441-7762, by mail (c/o BlackRock Funds, P.O. Box 9819, Providence, Rhode Island 02940-8019), or by the Internet at www.blackrock.com. The Fund’s initial and subsequent investment minimums generally are as follows, although the Fund may reduce or waive the minimums in some cases:

	Investor A and Investor C Shares	Institutional Shares
Minimum Initial Investment	$1,000 for all accounts except: • $50, if establishing an Automatic Investment Plan. • There is no investment minimum for employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs). • There is no investment minimum for certain fee-based programs.	There is no minimum initial investment for: • Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. • Clients of Financial Intermediaries that: (i) charge such clients a fee for advisory, investment consulting, or similar services or (ii) have entered into an agreement with the Fund’s distributor to offer Institutional Shares through a no-load program or investment platform. $2 million for individuals and “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts who may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. $1,000 for: • Clients investing through Financial Intermediaries that offer such shares on a platform that charges a transaction based sales commission outside of the Fund. • Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Fund’s distributor to offer Institutional Shares, and the family members of such persons.
Minimum Additional Investment	$50 for all accounts (with the exception of certain employer-sponsored retirement plans which may have a lower minimum).	No subsequent minimum.

Tax Information

The Fund’s dividends and distributions may be subject to U.S. federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor or are investing through a qualified tax-exempt plan described in section 401(a) of the Internal Revenue Code, in which case you may be subject to U.S. federal income tax when distributions are received from such tax-deferred arrangements.

The Fund intends to make distributions most of which will be excludable from gross income for federal income tax purposes.

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Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a Financial Intermediary, the Fund and BlackRock Investments, LLC, the Fund’s distributor, or its affiliates may pay the Financial Intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the Financial Intermediary and your individual financial professional to recommend the Fund over another investment.

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Fund Overview

Key Facts About BlackRock National Municipal Fund

Investment Objective

The investment objective of BlackRock National Municipal Fund (the “National Fund” or the “Fund”) is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Fees and Expenses of the Fund

Shareholder Fees (fees paid directly from your investment)		Investor A Shares		Investor C Shares		Institutional Shares
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)		4.25%		None		None
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)		None ¹		1.00% ²		None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)		Investor A Shares		Investor C Shares		Institutional Shares
Management Fee³		0.39%		0.39%		0.39%
Distribution and/or Service (12b-1) Fees		0.25%		1.00%		None
Other Expenses		0.18%		0.12%		0.14%
Interest Expense	0.05%		0.05%		0.05%
Miscellaneous Other Expenses	0.13%		0.07%		0.09%
Acquired Fund Fees and Expenses⁴		0.01%		0.01%		0.01%
Total Annual Fund Operating Expenses⁴		0.83%		1.52%		0.54%
Fee Waivers and/or Expense Reimbursements^3,5		(0.09)%		(0.03)%		(0.05)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^3,5		0.74%		1.49%		0.49%

¹	A contingent deferred sales charge (“CDSC”) of 1.00% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at the time of purchase as part of an investment of $250,000 or more.
²	There is no CDSC on Investor C Shares after one year.

⁴	The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses.

⁵

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 56, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.68% (for Investor A Shares), 1.43% (for Investor C Shares) and 0.43% (for Institutional Shares) of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

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Example:

	1 Year	3 Years	5 Years	10 Years
Investor A Shares	$497	$670	$857	$1,399
Investor C Shares	$252	$477	$826	$1,810
Institutional Shares	$ 50	$168	$297	$ 672

You would pay the following expenses if you did not redeem your shares:

	1 Year	3 Years	5 Years	10 Years
Investor C Shares	$152	$477	$826	$1,810

Portfolio Turnover:

Principal Investment Strategies of the Fund

Under normal circumstances, the National Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Although Fund management presently intends to invest at least 65% of the Fund’s net assets in municipal bonds rated investment grade or in unrated municipal bonds that Fund management believes are of comparable quality, it is possible that in the future the Fund could invest up to 100% of its assets in “junk bonds.” Investment grade bonds are securities which are rated in the four highest categories by at least one of the major rating agencies or determined by the management team to be of similar quality. The Fund does not intend to invest more than 35% of its net assets in junk bonds or in unrated bonds that Fund management believes are of comparable quality. This is a non-fundamental policy and may be changed by the Board at any time. The Fund will usually invest in municipal bonds that have a maturity of five years or longer.

The Fund may engage in transactions in certain derivatives, such as financial futures contracts and options thereon, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may leverage its assets through the use of proceeds received through tender option bond transactions. In a tender option bond transaction, the Fund transfers municipal bonds or other municipal securities into a special purpose entity (a “TOB Trust”). A TOB Trust typically issues two classes of beneficial interests: short-term floating rate interests (“TOB Floaters”), which are sold to third party investors, and residual inverse floating rate interests (“TOB Residuals”), which are generally issued to the Fund. The Fund may invest in TOB Residuals and may also invest in TOB Floaters. The Fund will look through to the underlying municipal bond held by a TOB Trust for purposes of the Fund’s 80% policy.

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Principal Risks of Investing in the Fund

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
■	Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
	Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
	Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.

Market and Illiquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.

Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.

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Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.

Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.

Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

■	Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

■

Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

■

Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:

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	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.
■	Tender Option Bonds and Related Securities Risk — The Fund’s participation in tender option bond transactions may reduce the Fund’s returns and/or increase volatility. Investments in tender option bond transactions expose the Fund to counterparty risk and leverage risk. An investment in a tender option bond transaction typically will involve greater risk than an investment in a municipal fixed rate security, including the risk of loss of principal. Distributions on TOB Residuals will bear an inverse relationship to short-term municipal security interest rates. Distributions on TOB Residuals paid to the Fund will be reduced or, in the extreme, eliminated as short-term municipal interest rates rise and will increase when short-term municipal interest rates fall. TOB Residuals generally will underperform the market for fixed rate municipal securities in a rising interest rate environment. The Fund may invest in TOB Trusts on either a non-recourse or recourse basis. If the Fund invests in a TOB Trust on a recourse basis, it could suffer losses in excess of the value of its TOB Residuals.

Performance Information

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Investor A Shares

ANNUAL TOTAL RETURNS

BlackRock National Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 7.42% (quarter ended September 30, 2009) and the lowest return for a quarter was -4.60% (quarter ended December 31, 2010). The year-to-date return as of September 30, 2019 was 6.42%.

As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock National Municipal Fund — Investor A Shares
Return Before Taxes	(3.91)%	2.85%	5.11%
Return After Taxes on Distributions	(3.91)%	2.85%	5.11%
Return After Taxes on Distributions and Sale of Fund Shares	(1.21)%	2.92%	4.88%
BlackRock National Municipal Fund — Investor C Shares
Return Before Taxes	(1.36)%	2.98%	4.79%
BlackRock National Municipal Fund — Institutional Shares
Return Before Taxes	0.61%	3.96%	5.77%
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
Custom National Index¹ (Reflects no deduction for fees, expenses or taxes)	1.20%	4.83%	5.47%

¹	The Custom National Index reflects the returns of the S&P^® Municipal Bond Index for periods prior to January 1, 2013, and the returns of only those bonds in the S&P^® Municipal Bond Index that have maturities greater than 5 years for periods subsequent to January 1, 2013.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Investor C and Institutional Shares will vary.

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Walter O’Connor, CFA	1996	Managing Director of BlackRock, Inc.
Michael Kalinoski, CFA	2016	Director of BlackRock, Inc.

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Purchase and Sale of Fund Shares

	Investor A and Investor C Shares	Institutional Shares
Minimum Initial Investment	$1,000 for all accounts except: • $50, if establishing an Automatic Investment Plan. • There is no investment minimum for employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs). • There is no investment minimum for certain fee-based programs.	There is no minimum initial investment for: • Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. • Clients of Financial Intermediaries that: (i) charge such clients a fee for advisory, investment consulting, or similar services or (ii) have entered into an agreement with the Fund’s distributor to offer Institutional Shares through a no-load program or investment platform. $2 million for individuals and “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts who may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. $1,000 for: • Clients investing through Financial Intermediaries that offer such shares on a platform that charges a transaction based sales commission outside of the Fund. • Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Fund’s distributor to offer Institutional Shares, and the family members of such persons.
Minimum Additional Investment	$50 for all accounts (with the exception of certain employer-sponsored retirement plans which may have a lower minimum).	No subsequent minimum.

Tax Information

The Fund intends to make distributions most of which will be excludable from gross income for federal income tax purposes.

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Payments to Broker/Dealers and Other Financial Intermediaries

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Fund Overview

Key Facts About BlackRock Short-Term Municipal Fund

Investment Objective

The investment objective of BlackRock Short-Term Municipal Fund (the “Short-Term Fund” or the “Fund”) is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock and its affiliates) (each a “Financial Intermediary”) and in the “Details About the Share Classes” and the “Intermediary-Defined Sales Charge Waiver Policies” sections on pages 41 and A-1, respectively, of the Fund’s prospectus and in the “Purchase of Shares” section on page II-84 of Part II of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Investor A Shares	Investor C Shares	Institutional Shares
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	3.00%	None	None
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)	None ¹	1.00% ²	None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Investor A Shares	Investor C Shares	Institutional Shares
Management Fee³	0.29%	0.29%	0.29%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	None
Other Expenses	0.13%	0.16%	0.17%
Total Annual Fund Operating Expenses	0.67%	1.45%	0.46%
Fee Waivers and/or Expense Reimbursements^3,4	(0.06)%	(0.09)%	(0.10)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^3,4	0.61%	1.36%	0.36%

¹	A contingent deferred sales charge (“CDSC”) of 0.25% is assessed on certain redemptions of Investor A Shares made within 9 months after purchase where no initial sales charge was paid at the time of purchase as part of an investment of $100,000 or more.

²	There is no CDSC on Investor C Shares after one year.

⁴

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 56, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.61% (for Investor A Shares), 1.36% (for Investor C Shares) and 0.36% (for Institutional Shares) of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

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return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Investor A Shares	$360	$502	$656	$1,104
Investor C Shares	$238	$450	$784	$1,728
Institutional Shares	$ 37	$138	$248	$ 569

You would pay the following expenses if you did not redeem your shares:

	1 Year	3 Years	5 Years	10 Years
Investor C Shares	$138	$450	$784	$1,728

Portfolio Turnover:

Principal Investment Strategies of the Fund

Under normal circumstances, the Short-Term Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The Short-Term Fund invests primarily in investment grade municipal bonds or municipal notes, including variable rate demand obligations. Investment grade bonds are securities which are rated in the four highest categories by at least one of the major rating agencies or determined by the management team to be of similar quality. Generally, the higher the rating of a bond, the higher the likelihood that interest and principal payments will be made on time. Municipal notes are shorter-term municipal debt obligations that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax) and that have a maturity that is generally one year or less.

The Fund will maintain a dollar weighted maturity of no more than two years. Because of their shorter maturities, the Fund’s investments will not usually be as sensitive to changes in prevailing interest rates as are long-term municipal bonds. Fluctuations in interest rates on short-term municipal bonds may, however, vary more widely from time to time than those on long-term municipal bonds.

Principal Risks of Investing in the Fund

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.

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	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

■	High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance.
■	Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

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■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

■

Variable Rate Demand Obligations Risk — Variable rate demand obligations are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution. If the bank or financial institution is unable to pay, the Fund may lose money.

Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the S&P^® Municipal Bond Index and the S&P^® Limited Maturity Municipal Bond Index, which are relevant to the Fund because they have characteristics similar to the Fund’s investment strategies. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

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Institutional Shares

ANNUAL TOTAL RETURNS

BlackRock Short-Term Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 1.57% (quarter ended March 31, 2009) and the lowest return for a quarter was -0.61% (quarter ended December 31, 2016). The year-to-date return as of September 30, 2019 was 1.81%.

As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock Short-Term Municipal Fund — Institutional Shares
Return Before Taxes	1.54%	0.60%	1.02%
Return After Taxes on Distributions	1.54%	0.60%	1.02%
Return After Taxes on Distributions and Sale of Fund Shares	1.46%	0.62%	1.01%
BlackRock Short-Term Municipal Fund — Investor A Shares
Return Before Taxes	(1.74)%	(0.27)%	0.45%
BlackRock Short-Term Municipal Fund — Investor C Shares
Return Before Taxes	(0.46)%	(0.44)%	(0.02)%
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
S&P ^® Limited Maturity Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.76%	1.00%	1.59%

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Kevin A. Schiatta, CFA	2016	Director of BlackRock, Inc.
Kristi Manidis	2019	Director of BlackRock, Inc.

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Purchase and Sale of Fund Shares

	Investor A and Investor C Shares	Institutional Shares
Minimum Initial Investment	$1,000 for all accounts except: • $50, if establishing an Automatic Investment Plan. • There is no investment minimum for employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs). • There is no investment minimum for certain fee-based programs.	There is no minimum initial investment for: • Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. • Clients of Financial Intermediaries that: (i) charge such clients a fee for advisory, investment consulting, or similar services or (ii) have entered into an agreement with the Fund’s distributor to offer Institutional Shares through a no-load program or investment platform. $2 million for individuals and “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts who may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares. $1,000 for: • Clients investing through Financial Intermediaries that offer such shares on a platform that charges a transaction based sales commission outside of the Fund. • Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Fund’s distributor to offer Institutional Shares, and the family members of such persons.
Minimum Additional Investment	$50 for all accounts (with the exception of certain employer-sponsored retirement plans which may have a lower minimum).	No subsequent minimum.

Tax Information

The Fund intends to make distributions most of which will be excludable from gross income for federal income tax purposes.

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Payments to Broker/Dealers and Other Financial Intermediaries

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Details About the Funds

Included in this prospectus are sections that tell you about buying and selling shares, management information, shareholder features of BlackRock High Yield Municipal Fund (the “High Yield Fund”), BlackRock National Municipal Fund (the “National Fund”) and BlackRock Short-Term Municipal Fund (the “Short-Term Fund”) (each a “Fund” and collectively, the “Funds”) and your rights as a shareholder.

How Each Fund Invests

Investment Process

With respect to each Fund, BlackRock Advisors, LLC (“BlackRock”) considers a variety of factors when choosing investments, such as:

■	Credit Quality of Issuers — based on bond ratings and other factors, including economic and financial conditions.
■	Yield Analysis — takes into account factors such as the different yields available on different types of obligations and the shape of the yield curve (longer term obligations typically have higher yields).
■	Maturity Analysis — the weighted average maturity of the portfolio will be maintained within a desirable range as determined from time to time. Factors considered include portfolio activity, maturity of the supply of available bonds and the shape of the yield curve. Maturity of a debt security refers to the date upon which debt securities are due to be repaid, that is, the date when the issuer generally must pay back the face amount of the security.

In choosing investments, Fund management analyzes the credit quality of issuers and considers the yields available on municipal bonds with different maturities. In addition, Fund management considers the availability of features that protect against an early call of a bond by the issuer.

The Funds intend to invest so that no more than 25% of a Fund’s assets are represented by the municipal securities of issuers located in the same state.

High Yield Fund

Investment Objective

The investment objective of the High Yield Fund is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Principal Investment Strategies

Under normal circumstances, the High Yield Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. This policy is a fundamental policy of the Fund and may not be changed without approval of a majority of the Fund’s outstanding voting securities, as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”). Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The High Yield Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Fund management chooses municipal bonds that it believes offer a relatively high potential for total return relative to their total risk. Although the Fund may invest in municipal bonds in any rating category, Fund management presently intends to invest at least 65% of the Fund’s net assets in medium- to low-quality bonds as rated by at least one independent rating agency (BBB or lower by S&P Global Ratings (“S&P”) or Fitch Ratings, Inc. (“Fitch”) or Baa or lower by Moody’s Investors Service, Inc. (“Moody’s”)), or if unrated, judged to be of comparable quality by BlackRock. Obligations rated below BBB or Baa are commonly known as “junk bonds.” It is possible that the Fund could invest up to 100% of its assets in junk bonds. Fund management reserves the right to invest less than 65% of the Fund’s net assets in

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municipal bonds rated BBB or Baa or lower if Fund management determines that there is an insufficient supply of such obligations available for investment.

The Fund may also invest up to 10% of its total assets in municipal bonds that are considered distressed securities, which are securities that are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest at the time of acquisition or are rated in the lowest rating categories by at least one independent rating agency (CC or lower by S&P or Fitch or Ca or lower by Moody’s), or if unrated, judged to be of comparable quality by BlackRock. The Fund will usually invest in municipal bonds that have a maturity of five years or longer. Generally, the Fund will invest in distressed securities when Fund management believes they offer significant potential for higher returns or can be exchanged for other securities that offer this potential. However, there can be no assurance that the Fund will achieve these returns or that the issuer will make an exchange offer or adopt a plan of reorganization.

ABOUT THE PORTFOLIO MANAGEMENT OF THE HIGH YIELD FUND

The Fund is managed by a team of financial professionals. Theodore R. Jaeckel, CFA and Walter O’Connor, CFA, are the portfolio managers and are jointly and primarily responsible for the day-to-day management of the Fund. Please see “Management of the Funds — Portfolio Manager Information” for additional information about the portfolio management team.

National Fund

Investment Objective

The investment objective of the National Fund is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund. This investment objective is a fundamental policy of the Fund and may not be changed without approval of a majority of the Fund’s outstanding voting securities, as defined in the Investment Company Act.

Principal Investment Strategies

Under normal circumstances, the National Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. This policy is a fundamental policy of the Fund and may not be changed without approval of a majority of the Fund’s outstanding securities, as defined in the Investment Company Act. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations. The Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds.

Fund management will choose municipal bond investments that it believes offer a relatively high potential for total return relative to their total risk. Although the Fund’s investment policies are not governed by specific rating categories, Fund management does not presently intend to invest more than 35% of the Fund’s assets in municipal bonds rated below investment grade (below BBB by S&P or Fitch, or below Baa by Moody’s) or in unrated municipal bonds that Fund management believes are of comparable quality. These lower-rated obligations are commonly known as “junk bonds.” The 35% limitation on junk bond investments reflects only the present intention of Fund management, and may be changed at any time by the Board without shareholder approval. Therefore, it is possible that the Fund could invest up to 100% of its assets in junk bonds. The Fund will not invest in municipal bonds rated in the lowest rating categories (CC or lower by S&P or Fitch, or Ca or lower by Moody’s) unless Fund management believes those ratings do not accurately reflect the financial condition of the issuer or other factors affecting the creditworthiness of the bonds. Fund management does not presently intend to invest in municipal bonds that are in default or that it believes will be in default. The Fund will usually invest in municipal bonds that have a maturity of five years or longer.

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returns. Derivatives allow the Fund to increase or decrease its risk exposure more quickly and efficiently than other types of instruments. The Fund is not required to use hedging and may choose not to do so.

The Fund may leverage its assets through the use of proceeds received through tender option bond transactions. In a tender option bond transaction, the Fund transfers municipal bonds or other municipal securities into a special purpose entity (a “TOB Trust”). A TOB Trust typically issues two classes of beneficial interests: short-term floating rate interests (“TOB Floaters”), which are sold to third party investors, and residual inverse floating rate interests (“TOB Residuals”), which are generally issued to the Fund. The Fund may invest in TOB Residuals and may also invest in TOB Floaters. The Fund will look through to the underlying municipal bond held by a TOB Trust for purposes of the Fund’s 80% policy. TOB Trusts have historically been established by third party sponsors (e.g., banks, broker-dealers and other financial institutions). Rules implementing section 619 of the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Volcker Rule”) may preclude banking entities and their affiliates from sponsoring TOB Trusts as such Trusts have been structured prior to the effective date of the Volcker Rule. In response to these restrictions, market participants have developed a new structure for TOB Trusts designed to ensure that no banking entity is sponsoring the TOB Trust for purposes of the Volcker Rule.

ABOUT THE PORTFOLIO MANAGEMENT OF THE NATIONAL FUND

The Fund is managed by a team of financial professionals. Walter O’Connor, CFA, and Michael Kalinoski, CFA are the portfolio managers and are jointly and primarily responsible for the day-to-day management of the Fund. Please see “Management of the Funds — Portfolio Manager Information” for additional information about the portfolio management team.

Short-Term Fund

Investment Objective

The investment objective of the Short-Term Fund is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund. This investment objective is a fundamental policy of the Fund and may not be changed without approval of a majority of the Fund’s outstanding voting securities, as defined in the Investment Company Act.

Principal Investment Strategies

Under normal circumstances, the Short-Term Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. This policy is a fundamental policy of the Fund and may not be changed without approval of a majority of the Fund’s outstanding securities, as defined in the Investment Company Act. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

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ABOUT THE PORTFOLIO MANAGEMENT OF THE SHORT-TERM FUND

The Fund is managed by a team of financial professionals. Kevin Schiatta, CFA, and Kristi Manidis, are the portfolio managers and are jointly and primarily responsible for the day-to-day management of the Fund. Please see “Management of the Funds — Portfolio Manager Information” for additional information about the portfolio management team.

Other Strategies

In addition to the principal strategies discussed above, each Fund may also invest or engage in the following investments/strategies:

■

Borrowing — Each Fund may borrow for temporary or emergency purposes, including to meet redemptions, for the payment of dividends, for share repurchases or for the clearance of transactions, subject to the limits set forth under the Investment Company Act, the rules and regulations thereunder and any applicable exemptive relief.

■	Indexed Securities — Each Fund may invest in securities the potential return of which is directly related to changes in an underlying index or interest rate, known as indexed securities. The return on indexed securities will rise when the underlying index rises and fall when the index falls.
■	Investment Companies — Each Fund has the ability to invest in other investment companies, such as exchange-traded funds, unit investment trusts, and open-end and closed-end funds. Each Fund may invest in affiliated investment companies, including affiliated money market funds and affiliated exchange-traded funds.

■

Restricted Securities — Restricted securities are securities that cannot be offered for public resale unless registered under the applicable securities laws or that have a contractual restriction that prohibits or limits their resale. They may include Rule 144A securities, which are privately placed securities that can be resold to qualified institutional buyers but not to the general public, and securities of U.S. and non-U.S. issuers that are offered pursuant to Regulation S under the Securities Act of 1933, as amended.

■	Securities Lending — Each Fund may lend securities with a value up to 33¹⁄3% of its total assets to financial institutions that provide cash or securities issued or guaranteed by the U.S. Government as collateral.
■	Taxable Income — Investments in taxable money market securities as well as some of the derivatives discussed herein may cause a Fund to have taxable investment income. Each Fund may also realize capital gains on the sale of its municipal bonds (and other securities it holds). These capital gains will be taxable regardless of whether they are derived from a sale of municipal bonds.
■	Taxable Money Market Securities — Each Fund may invest up to 20% of its assets on a temporary basis in taxable money market securities that have a maturity of one year or less. Each Fund may make these investments for liquidity purposes or as a temporary investment pending an investment in municipal bonds.
■	Temporary Defensive Strategies — As a temporary measure for defensive purposes, a Fund may invest without limitation in taxable money market securities. These investments may prevent a Fund from meeting its investment objective.
■	When-Issued and Delayed Delivery Securities and Forward Commitments — The purchase or sale of securities on a when-issued basis, on a delayed delivery basis or through a forward commitment involves the purchase or sale of securities by a Fund at an established price with payment and delivery taking place in the future. Each Fund enters into these transactions to obtain what is considered an advantageous price to the Fund at the time of entering into the transaction.

High Yield Fund Other Strategies

■

Derivatives — The High Yield Fund is permitted to engage in transactions in certain derivatives, such as financial futures contracts and options thereon, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. Derivatives are financial instruments whose value is derived from another security or an index such as the S&P Municipal Bond Index. The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. Derivatives allow the Fund to increase or decrease its risk exposure more quickly and efficiently than other types of instruments. The Fund is not required to use hedging and may choose not to do so.

■

Tender Option Bonds and Related Securities — The High Yield Fund may leverage its assets through the use of proceeds received through tender option bond transactions. In a tender option bond transaction, the Fund transfers municipal bonds or other municipal securities into a special purpose entity (a “TOB Trust”). A TOB Trust typically issues two classes of beneficial interests: short-term floating rate interests (“TOB Floaters”), which are sold to third party investors, and residual inverse floating rate interests (“TOB Residuals”), which are generally issued to the

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	Fund. The Fund may invest in TOB Residuals and may also invest in TOB Floaters. The Fund will look through to the underlying municipal bond held by a TOB Trust for purposes of the Fund’s 80% policy.
■	Variable Rate Demand Obligations — The High Yield Fund may invest in variable rate demand obligations, which are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution.

National Fund Other Strategies

■	Variable Rate Demand Obligations — The National Fund may invest in variable rate demand obligations, which are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution.

Short-Term Fund Other Strategies

■

Derivatives — The Short-Term Fund may engage in transactions in certain derivatives, such as financial futures contracts and options thereon, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. Derivatives are financial instruments whose value is derived from another security or an index such as the S&P Municipal Bond Index. The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. Derivatives allow the Fund to increase or decrease its risk exposure more quickly and efficiently than other types of instruments. The Fund is not required to use hedging and may choose not to do so.

Investment Risks

This section contains a discussion of the general risks of investing in the Funds. The “Investment Objectives and Policies” section in the Statement of Additional Information (“SAI”) also includes more information about each Fund, its investments and the related risks. As with any fund, there can be no guarantee that a Fund will meet its investment objective or that a Fund’s performance will be positive for any period of time. An investment in a Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or by any bank or governmental agency. Each risk noted below is applicable to each Fund unless the specific Fund or Funds are noted in parentheticals. The order of the below risk factors does not indicate the significance of any particular risk factor.

Principal Risks of Investing in a Fund:

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.

Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.

The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.

To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.

These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.

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monetary stimulus program known as quantitative easing, the Federal Reserve has purchased on the open market large quantities of securities issued or guaranteed by the U.S. Government, its agencies or instrumentalities. As the Federal Reserve “tapers” or reduces the amount of securities it purchases pursuant to quantitative easing, and/or if the Federal Reserve raises the federal funds rate, there is a risk that interest rates will rise. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from mutual funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.

During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns. Certain countries have recently experienced negative interest rates on certain fixed-income instruments. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, may result in heightened market volatility and may detract from Fund performance to the extent the Fund is exposed to such interest rates.

Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.

Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. Rising interest rates tend to extend the duration of securities, making them more sensitive to changes in interest rates. The value of longer-term securities generally changes more in response to changes in interest rates than shorter-term securities. As a result, in a period of rising interest rates, securities may exhibit additional volatility and may lose value.

Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields. In periods of falling interest rates, the rate of prepayments tends to increase (as does price fluctuation) as borrowers are motivated to pay off debt and refinance at new lower rates. During such periods, reinvestment of the prepayment proceeds by the management team will generally be at lower rates of return than the return on the assets that were prepaid. Prepayment reduces the yield to maturity and the average life of the security.

■	Derivatives Risk (National Fund Principal Risk; High Yield Fund and Short-Term Fund Other Risk) — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
	Volatility Risk — The Fund’s use of derivatives may reduce the Fund’s returns and/or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
	Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.

Market and Illiquidity Risk — Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, BlackRock may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.

Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them. Derivatives may also expose the Fund to greater risk and increase its costs. Certain transactions in derivatives involve substantial leverage risk and may expose the Fund to potential losses that exceed the amount originally invested by the Fund.

Hedging Risk — When a derivative is used as a hedge against a position that the Fund holds, any loss generated by the derivative generally should be substantially offset by gains on the hedged investment, and vice versa. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences noted below.

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Tax Risk — The federal income tax treatment of a derivative may not be as favorable as a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments. As a result, a larger portion of the Fund’s distributions may be treated as ordinary income rather than as tax-exempt income or as capital gains. In addition, certain derivatives are subject to mark-to-market or straddle provisions of the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). If such provisions are applicable, there could be an increase (or decrease) in the amount of taxable dividends paid by the Fund. Payments received by the Fund from swap agreements, if any, will generally produce taxable income, while payments made by the Fund on swap agreements will be allocated against both tax-exempt and taxable gross income, decreasing the Fund’s distributable net tax-exempt income. In addition, the tax treatment of certain derivatives, such as swaps, is unsettled and may be subject to future legislation, regulation or administrative pronouncements issued by the Internal Revenue Service (the “IRS”).

Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

Future regulatory developments may impact the Fund’s ability to invest or remain invested in certain derivatives. Legislation or regulation may also change the way in which the Fund itself is regulated. BlackRock cannot predict the effects of any new governmental regulation that may be implemented on the ability of the Fund to use swaps or any other financial derivative product, and there can be no assurance that any new governmental regulation will not adversely affect the Fund’s ability to achieve its investment objective.

Risks Specific to Certain Derivatives Used by the Fund

Swaps — Swap agreements, including total return swaps that may be referred to as contracts for difference, are two-party contracts entered into for periods ranging from a few weeks to more than one year. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments, which can be adjusted for an interest factor. Swap agreements involve the risk that the party with whom the Fund has entered into the swap will default on its obligation to pay the Fund and the risk that the Fund will not be able to meet its obligations to pay the other party to the agreement. Swap agreements may also involve the risk that there is an imperfect correlation between the return on the Fund’s obligation to its counterparty and the return on the referenced asset. In addition, swap agreements are subject to market and illiquidity risk, leverage risk and hedging risk.

Credit Default Swaps — Credit default swaps may have as reference obligations one or more securities that are not currently held by the Fund. The protection “buyer” may be obligated to pay the protection “seller” an up-front payment or a periodic stream of payments over the term of the contract, provided generally that no credit event on a reference obligation has occurred. Credit default swaps involve special risks in addition to those mentioned above because they are difficult to value, are highly susceptible to illiquid investments risk and credit risk, and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty).

Futures — Futures are standardized, exchange-traded contracts that obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of an asset at a specified future date at a specified price. The primary risks associated with the use of futures contracts and options are: (a) the imperfect correlation between the change in market value of the instruments held by the Fund and the price of the futures contract or option; (b) the possible lack of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (c) losses caused by unanticipated market movements, which are potentially unlimited; (d) the investment adviser’s inability to predict correctly the direction of securities prices, interest

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rates, currency exchange rates and other economic factors; and (e) the possibility that the counterparty will default in the performance of its obligations.

Options — An option is an agreement that, for a premium payment or fee, gives the option holder (the purchaser) the right but not the obligation to buy (a “call option”) or sell (a “put option”) the underlying asset (or settle for cash in an amount based on an underlying asset, rate, or index) at a specified price (the “exercise price”) during a period of time or on a specified date. Investments in options are considered speculative. When the Fund purchases an option, it may lose the total premium paid for it if the price of the underlying security or other assets decreased, remained the same or failed to increase to a level at or beyond the exercise price (in the case of a call option) or increased, remained the same or failed to decrease to a level at or below the exercise price (in the case of a put option). If a put or call option purchased by the Fund were permitted to expire without being sold or exercised, its premium would represent a loss to the Fund. To the extent that the Fund writes or sells an option, if the decline or increase in the underlying asset is significantly below or above the exercise price of the written option, the Fund could experience a substantial loss.

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Distressed Securities Risk (High Yield Fund) — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

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High Portfolio Turnover Risk (Short-Term Fund) — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance.

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Junk Bonds Risk (High Yield Fund and National Fund) — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund. The major risks of junk bond investments include:

■	Junk bonds may be issued by less creditworthy issuers. Issuers of junk bonds may have a larger amount of outstanding debt relative to their assets than issuers of investment grade bonds. In the event of an issuer’s bankruptcy, claims of other creditors may have priority over the claims of junk bond holders, leaving few or no assets available to repay junk bond holders.
■	Prices of junk bonds are subject to extreme price fluctuations. Adverse changes in an issuer’s industry and general economic conditions may have a greater impact on the prices of junk bonds than on other higher rated fixed-income securities.
■	Issuers of junk bonds may be unable to meet their interest or principal payment obligations because of an economic downturn, specific issuer developments, or the unavailability of additional financing.

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■	Junk bonds frequently have redemption features that permit an issuer to repurchase the security from the Fund before it matures. If the issuer redeems junk bonds, the Fund may have to invest the proceeds in bonds with lower yields and may lose income.

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Junk bonds may be less liquid than higher rated fixed-income securities, even under normal economic conditions. There are fewer dealers in the junk bond market, and there may be significant differences in the prices quoted for junk bonds by the dealers. Because they are less liquid than higher rated fixed-income securities, judgment may play a greater role in valuing junk bonds than is the case with securities trading in a more liquid market.

■	The Fund may incur expenses to the extent necessary to seek recovery upon default or to negotiate new terms with a defaulting issuer.

The credit rating of a high yield security does not necessarily address its market value risk. Ratings and market value may change from time to time, positively or negatively, to reflect new developments regarding the issuer.

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Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose a Fund to greater risk and increase its costs. As an open-end investment company registered with the Securities and Exchange Commission (the “SEC”), the Fund is subject to the federal securities laws, including the Investment Company Act, the rules thereunder, and various SEC and SEC staff interpretive positions. In accordance with these laws, rules and positions, the Fund must “set aside” liquid assets (often referred to as “asset segregation”), or engage in other SEC- or staff-approved measures, to “cover” open positions with respect to certain kinds of instruments. The use of leverage may cause a Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of a Fund’s portfolio will be magnified when the Fund uses leverage.

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — The full faith, credit and taxing power of the municipality that issues a general obligation bond secures payment of interest and repayment of principal. Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — Payments of interest and principal on revenue bonds are made only from the revenues generated by a particular facility, class of facilities or the proceeds of a special tax or other revenue source. These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its full faith, credit and taxing power for repayment. If the private enterprise defaults on its payments, the Fund may not receive any income or get its money back from the investment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. They may provide interim financing in anticipation of, and are secured by, tax collection, bond sales or revenue receipts. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. The issuer will generally appropriate municipal funds for that purpose, but is not obligated to do so. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property. However, if the issuer does not fulfill its payment obligation it may be difficult to sell the property and the proceeds of a sale may not cover the Fund’s loss.
	Tax-Exempt Status Risk — In making investments, the Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal obligations and payments under tax-exempt derivative securities. Neither the Fund nor its

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	investment manager will independently review the bases for those tax opinions. If any of those tax opinions are ultimately determined to be incorrect or if events occur after the security is acquired that impact the security’s tax-exempt status, the Fund and its shareholders could be subject to substantial tax liabilities. The IRS has generally not ruled on the taxability of the securities. An assertion by the IRS that a portfolio security is not exempt from U.S. federal income tax (contrary to indications from the issuer) could affect the Fund’s and its shareholders’ income tax liability for the current or past years and could create liability for information reporting penalties. In addition, an IRS assertion of taxability may impair the liquidity and the fair market value of the securities.
■	Tender Option Bonds and Related Securities Risk (National Fund Principal Risk; High Yield Fund Other Risk) — The Fund’s participation in tender option bond transactions may reduce the Fund’s returns and/or increase volatility. Investments in tender option bond transactions expose the Fund to counterparty risk and leverage risk. An investment in a tender option bond transaction typically will involve greater risk than an investment in a municipal fixed rate security, including the risk of loss of principal. Distributions on TOB Residuals will bear an inverse relationship to short-term municipal security interest rates. Distributions on TOB Residuals paid to the Fund will be reduced or, in the extreme, eliminated as short-term municipal interest rates rise and will increase when short-term municipal interest rates fall. TOB Residuals generally will underperform the market for fixed rate municipal securities in a rising interest rate environment.
	The Fund may invest in TOB Trusts on either a non-recourse or recourse basis. TOB Trusts are typically supported by a liquidity facility provided by a third-party bank or other financial institution (the “Liquidity Provider”) that allows the holders of the TOB Floaters to tender their certificates in exchange for payment of par plus accrued interest on any business day, subject to the non-occurrence of tender option termination events. When the Fund invests in a TOB Trust on a non-recourse basis, and the Liquidity Provider is required to make a payment under the liquidity facility, the Liquidity Provider will typically liquidate all or a portion of the municipal securities held in the TOB Trust and then fund the balance, if any, of the amount owed under the liquidity facility over the liquidation proceeds (the “Liquidation Shortfall”).
	If a Fund invests in a TOB Trust on a recourse basis, the Fund will typically enter into a reimbursement agreement with the Liquidity Provider where the Fund is required to reimburse the Liquidity Provider the amount of any Liquidation Shortfall. As a result, if the Fund invests in a TOB Trust on a recourse basis, the Fund will bear the risk of loss with respect to any Liquidation Shortfall.
	To the extent that the Fund, rather than a third-party bank or financial institution, sponsors a TOB Trust, certain responsibilities that previously belonged to the sponsor bank will be performed by, or on behalf of, the Fund. The Fund’s additional duties and responsibilities under the new TOB Trust structure may give rise to certain additional risks including compliance, securities law and operational risks.

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Variable Rate Demand Obligations Risk (Short-Term Fund Principal Risk; High Yield Fund and National Fund Other Risk) — Variable rate demand obligations are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution. If the bank or financial institution is unable to pay, the Fund may lose money.

A Fund may also be subject to certain other non-principal risks associated with its investments and investment strategies, including:

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Borrowing Risk — Borrowing may exaggerate changes in the net asset value of Fund shares and in the return on the Fund’s portfolio. Borrowing will cost the Fund interest expense and other fees. The costs of borrowing may reduce the Fund’s return. Borrowing may cause the Fund to liquidate positions when it may not be advantageous to do so to satisfy its obligations.

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Cyber Security Risk — Failures or breaches of the electronic systems of the Fund, the Fund’s adviser, distributor, and other service providers, or the issuers of securities in which the Fund invests have the ability to cause disruptions and negatively impact the Fund’s business operations, potentially resulting in financial losses to the Fund and its shareholders. While the Fund has established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans and systems. Furthermore, the Fund cannot control the cyber security plans and systems of the Fund’s service providers or issuers of securities in which the Fund invests.

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Expense Risk — Fund expenses are subject to a variety of factors, including fluctuations in the Fund’s net assets. Accordingly, actual expenses may be greater or less than those indicated. For example, to the extent that the Fund’s net assets decrease due to market declines or redemptions, the Fund’s expenses will increase as a percentage of Fund net assets. During periods of high market volatility, these increases in the Fund’s expense ratio could be significant.

■	Indexed and Inverse Securities Risk — Indexed and inverse securities provide a potential return based on a particular index of value or interest rates. The Fund’s return on these securities will be subject to risk with respect

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to the value of the particular index. These securities are subject to leverage risk and correlation risk. Certain indexed and inverse securities have greater sensitivity to changes in interest rates or index levels than other securities, and the Fund’s investment in such instruments may decline significantly in value if interest rates or index levels move in a way Fund management does not anticipate.

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Investment in Other Investment Companies Risk — As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. In addition, if the Fund acquires shares of investment companies, including ones affiliated with the Fund, shareholders bear both their proportionate share of expenses in the Fund (including management and advisory fees) and, indirectly, the expenses of the investment companies (to the extent not offset by BlackRock through waivers). To the extent the Fund is held by an affiliated fund, the ability of the Fund itself to hold other investment companies may be limited.

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Municipal Securities Concentration Risk — From time to time the Fund may invest a substantial amount of its assets in municipal securities whose interest is paid solely from revenues of similar projects. If the Fund concentrates its investments in this manner, it assumes the legal and economic risks relating to such projects and this may have a significant impact on the Fund’s investment performance.

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Restricted Securities Risk — Limitations on the resale of restricted securities may have an adverse effect on their marketability, and may prevent the Fund from disposing of them promptly at advantageous prices. Restricted securities may not be listed on an exchange and may have no active trading market. In order to sell such securities, the Fund may have to bear the expense of registering the securities for resale and the risk of substantial delays in effecting the registration. Other transaction costs may be higher for restricted securities than unrestricted securities. Restricted securities may be difficult to value because market quotations may not be readily available, and the securities may have significant volatility. Also, the Fund may get only limited information about the issuer of a given restricted security, and therefore may be less able to predict a loss. Certain restricted securities may involve a high degree of business and financial risk and may result in substantial losses to the Fund.

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Securities Lending Risk — Securities lending involves the risk that the borrower may fail to return the securities in a timely manner or at all. As a result, the Fund may lose money and there may be a delay in recovering the loaned securities. The Fund could also lose money if it does not recover the securities and/or the value of the collateral falls, including the value of investments made with cash collateral. These events could trigger adverse tax consequences for the Fund.

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Taxability Risk — The Fund intends to minimize the payment of taxable income to shareholders by investing in tax-exempt or municipal securities in reliance at the time of purchase on an opinion of bond counsel to the issuer that the interest paid on those securities will be excludable from gross income for U.S. federal income tax purposes. Such securities, however, may be determined to pay, or have paid, taxable income subsequent to the Fund’s acquisition of the securities. In that event, the IRS may demand that the Fund pay U.S. federal income taxes on the affected interest income, and, if the Fund agrees to do so, the Fund’s yield could be adversely affected. In addition, the treatment of dividends previously paid or to be paid by the Fund as “exempt interest dividends” could be adversely affected, subjecting the Fund’s shareholders to increased U.S. federal income tax liabilities. If the interest paid on any tax-exempt or municipal security held by the Fund is subsequently determined to be taxable, the Fund will dispose of that security as soon as reasonably practicable. In addition, future laws, regulations, rulings or court decisions may cause interest on municipal securities to be subject, directly or indirectly, to U.S. federal income taxation or interest on state municipal securities to be subject to state or local income taxation, or the value of state municipal securities to be subject to state or local intangible personal property tax, or may otherwise prevent the Fund from realizing the full current benefit of the tax-exempt status of such securities. Any such change could also affect the market price of such securities, and thus the value of an investment in the Fund.

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Valuation Risk — The price the Fund could receive upon the sale of any particular portfolio investment may differ from the Fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation methodology or a price provided by an independent pricing service. As a result, the price received upon the sale of an investment may be less than the value ascribed by the Fund, and the Fund could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. Pricing services that value fixed-income securities generally utilize a range of market-based and security-specific inputs and assumptions, as well as considerations about general market conditions, to establish a price. Pricing services generally value fixed-income securities assuming orderly transactions of an institutional round lot size, but may be held or transactions may be conducted in such securities in smaller, odd lot sizes. Odd lots may trade at lower prices than institutional round lots. The Fund’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers.

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not meet its obligation. If this occurs, the Fund may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.

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Account Information

How to Choose the Share Class that Best Suits Your Needs

Each Fund currently offers multiple share classes (Investor A, Investor C and Institutional Shares in this prospectus), each with its own sales charge and expense structure, allowing you to invest in the way that best suits your needs. Each share class represents an ownership interest in the same investment portfolio of a Fund. When you choose your class of shares, you should consider the size of your investment and how long you plan to hold your shares. Either your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock and its affiliates) (each a “Financial Intermediary”) can help you determine which share class is best suited to your personal financial goals. Investor A Shares and Investor C Shares are sometimes referred to herein collectively as “Investor Shares.”

For example, if you select Institutional Shares, you will not pay any sales charge. However, only certain investors may buy Institutional Shares. If you select Investor A Shares, you generally pay a sales charge at the time of purchase and an ongoing service fee of 0.25% per year. You may be eligible for a sales charge reduction or waiver.

If you select Investor C Shares, you will invest the full amount of your purchase price, but you will be subject to a distribution fee of 0.75% per year for Investor C Shares, and a service fee of 0.25% per year for Investor C Shares under plans adopted pursuant to Rule 12b-1 under the Investment Company Act. Because these fees are paid out of a Fund’s assets on an ongoing basis, over time these fees increase the cost of your investment and may cost you more than paying other types of sales charges. In addition, you may be subject to a deferred sales charge when you sell Investor C Shares within one year. Classes with lower expenses will have higher net asset values and dividends relative to other share classes.

The Fund’s shares are distributed by BlackRock Investments, LLC (the “Distributor”), an affiliate of BlackRock.

The table below summarizes key features of each of the share classes of the Funds.

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Share Classes at a Glance¹

	Investor A	Investor C^2,3	Institutional
Availability	Generally available through Financial Intermediaries.	Generally available through Financial Intermediaries.	Limited to certain investors, including: • Individuals and “Institutional Investors” which include, but are not limited to endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts, who may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares. • Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares. • Employees, officers and directors/trustees of BlackRock or its affiliates and immediate family members of such persons, if they open an account directly with BlackRock. • Participants in certain programs sponsored by BlackRock or its affiliates or other Financial Intermediaries. • Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Distributor to offer Institutional Shares, and the family members of such persons. • Clients investing through Financial Intermediaries that have entered into an agreement with the Distributor to offer such shares on a platform that charges a transaction based sales commission outside of the Fund.

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	Investor A	Investor C^2,3	Institutional
Minimum Investment	$1,000 for all accounts except: • $50, if establishing an Automatic Investment Plan (“AIP”). • There is no investment minimum for employer-sponsored retirement plans (not including SEP IRAs, SIMPLE, IRAs or SARSEPs). • There is no investment minimum for certain fee-based programs.	$1,000 for all accounts except: • $50, if establishing an AIP. • There is no investment minimum for employer-sponsored retirement plans (not including SEP IRAs, SIMPLE, IRAs or SARSEPs). • There is no investment minimum for certain fee-based programs.	There is no investment minimum for: • Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies. • Employees, officers and directors/trustees of BlackRock or its affiliates and immediate family members of such persons, if they open an account directly with BlackRock. • Clients of Financial Intermediaries that: i) charge such clients a fee for advisory, investment consulting, or similar services or ii) have entered into an agreement with the Distributor to offer Institutional Shares through a no-load program or investment platform. $2 million for individuals and Institutional Investors. $1,000 investment minimum for: • Clients investing through Financial Intermediaries that offer such shares on a platform that charges a transaction based sales commission outside of the Fund. • Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Fund’s distributor to offer Institutional Shares, and the family members of such persons.
Initial Sales Charge?	Yes. Payable at time of purchase. Lower sales charges are available for larger investments.	No. Entire purchase price is invested in shares of a Fund.	No. Entire purchase price is invested in shares of a Fund.
Deferred Sales Charge?	No. (May be charged for purchases of $250,000 or more (for the High Yield Fund and the National Fund) or $100,000 or more (for the Short-Term Fund) that are redeemed within 18 months (for the High Yield Fund and the National Fund) or 9 months (for the Short-Term Fund)).	Yes. Payable if you redeem within one year of purchase.	No.

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	Investor A	Investor C^2,3	Institutional
Distribution and Service (12b-1) Fees?	No Distribution Fee. 0.25% Annual Service Fee.	0.75% Annual Distribution Fee. 0.25% Annual Service Fee.	No.
Redemption Fees?	No.	No.	No.
Conversion to Investor A Shares?	N/A	Yes, automatically approximately ten years after the date of purchase. It is the Financial Intermediary’s responsibility to ensure that the shareholder is credited with the proper holding period. As of the Effective Date (as defined below), certain Financial Intermediaries, including group retirement recordkeeping platforms, may not have been tracking such holding periods and therefore may not be able to process such conversions. In such instances, the automatic conversion of Investor C Shares to Investor A Shares will occur ten years after the Effective Date.	No.
Advantage	Makes sense for investors who are eligible to have the sales charge reduced or eliminated or who have a long-term investment horizon because there are no ongoing distribution fees.	No up-front sales charge so you start off owning more shares. These shares may make sense for investors who have a shorter investment horizon relative to Investor A Shares.	No up-front sales charge so you start off owning more shares. No distribution or service fees.
Disadvantage	You pay a sales charge up-front, and therefore you start off owning fewer shares.	You pay ongoing distribution fees each year you own Investor C Shares, which means that over the long term you can expect higher total fees per share than Investor A Shares and, as a result, lower total performance.	Limited availability.

¹	Please see “Details About the Share Classes” for more information about each share class.
²	If you establish a new account directly with a Fund and do not have a Financial Intermediary associated with your account, you may only invest in Investor A Shares. Applications without a Financial Intermediary that select Investor C Shares will not be accepted.
³	A Fund will not accept a purchase order of $500,000 or more for Investor C Shares (may be lower on funds that have set a lower breakpoint for purchasing Investor A Shares without a front-end sales charge). Your Financial Intermediary may set a lower maximum for Investor C Shares.

The following pages will cover the additional details of each share class, including the Institutional Shares requirements, the sales charge table for Investor A Shares, reduced sales charge information, Investor C Share CDSC information, and sales charge waivers.

The availability of certain sales charge waivers and reductions will depend on whether you purchase your shares directly from a Fund or through a Financial Intermediary. Financial Intermediaries may have different policies and procedures regarding the availability of front-end sales charge waivers or deferred sales charge waivers, which are discussed below. In all instances, it is your responsibility to notify the Fund or your Financial Intermediary at the time of purchase of any relationship or other facts qualifying you for sales charge waivers or reductions. For waivers and discounts not available through a particular Financial Intermediary, shareholders will have to purchase Fund shares directly from the Fund or through another Financial Intermediary to receive these waivers or reductions. Please see the “Intermediary-Defined Sales Charge Waiver Policies” section to determine any sales charge waivers and reductions that may be available to you through your Financial Intermediary.

More information about existing sales charge reductions and waivers is available free of charge in a clear and prominent format via hyperlink at www.blackrock.com and in the SAI, which is available on the website or on request.

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Details About the Share Classes

Investor A Shares — Initial Sales Charge Option

The following table shows the front-end sales charges that you may pay if you buy Investor A Shares. The offering price for Investor A Shares includes any front-end sales charge. The front-end sales charge expressed as a percentage of the offering price may be higher or lower than the charge described below due to rounding. Similarly, any contingent deferred sales charge paid upon certain redemptions of Investor A Shares expressed as a percentage of the applicable redemption amount may be higher or lower than the charge described below due to rounding. You may qualify for a reduced front-end sales charge. Purchases of Investor A Shares at certain fixed dollar levels, known as “breakpoints,” cause a reduction in the front-end sales charge. Once you achieve a breakpoint, you pay that sales charge on your entire purchase amount (and not just the portion above the breakpoint). If you select Investor A Shares, you will pay a sales charge at the time of purchase as shown in the following tables.

High Yield Fund and National Fund

Your Investment	Sales Charge As a % of Offering Price	Sales Charge As a % of Your Investment¹	Dealer Compensation As a % of Offering Price
Less than $100,000	4.25%	4.44%	4.00%
$100,000 but less than $250,000	3.25%	3.36%	3.00%
$250,000 and over²	0.00%	0.00%	— ²

Short-Term Fund

Your Investment	Sales Charge As a % of Offering Price	Sales Charge As a % of Your Investment¹	Dealer Compensation As a % of Offering Price
Less than $50,000	3.00%	3.09%	2.75%
$50,000 but less than $100,000	2.75%	2.83%	2.50%
$100,000 and over²	0.00%	0.00%	— ²

Rounded to the nearest one-hundredth percent.

If you invest $250,000 or more (for the High Yield Fund and the National Fund) or $100,000 or more (for the Short-Term Fund) in Investor A Shares, you will not pay an initial sales charge. In that case, BlackRock compensates the Financial Intermediary from its own resources. However, if you redeem your shares within 18 months (for the High Yield Fund and the National Fund) or 9 months (for the Short-Term Fund) after purchase, you may be charged a deferred sales charge of 1.00% (for the High Yield Fund and the National Fund) or 0.25% (for the Short-Term Fund) of the lesser of the original cost of the shares being redeemed or your redemption proceeds. Such deferred sales charge may be waived in connection with certain fee-based programs.

No initial sales charge applies to Investor A Shares that you buy through reinvestment of Fund dividends or capital gains.

Sales Charges Reduced or Eliminated for Investor A Shares

There are several ways in which the sales charge can be reduced or eliminated. Purchases of Investor A Shares at certain fixed dollar levels, known as “breakpoints,” cause a reduction in the front-end sales charge (as described above in the “Investor A Shares — Initial Sales Charge Option” section). Additionally, the front-end sales charge can be reduced or eliminated through one or a combination of the following: a Letter of Intent, the right of accumulation, the reinstatement privilege (described under “Account Services and Privileges”), or a waiver of the sales charge (described below).

Reductions or eliminations through a Letter of Intent or right of accumulation will apply to the value of all qualifying holdings in shares of mutual funds sponsored and advised by BlackRock or its affiliates (“BlackRock Funds”) owned by (a) the investor, or (b) the investor’s spouse and any children and a trust, custodial account or fiduciary account for the benefit of any such individuals. For this purpose, the value of an investor’s holdings means the offering price of the newly purchased shares (including any applicable sales charge) plus the current value (including any sales charges paid) of all other shares the investor already holds taken together.

See the “Intermediary-Defined Sales Charge Waiver Policies” section for sales charge reductions and waivers that may be available to customers of certain Financial Intermediaries.

Qualifying Holdings — Investor A and A1, Investor C, C1, C2 and C3, Investor P, Institutional, Class K and Premier Shares (in most BlackRock Funds), investments in certain unlisted closed-end management investment companies

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sponsored and advised by BlackRock or its affiliates (“Eligible Unlisted BlackRock Closed-End Funds”) and investments in the BlackRock CollegeAdvantage 529 Program.

Qualifying Holdings may include shares held in accounts held at a Financial Intermediary, including personal accounts, certain retirement accounts, UGMA/UTMA accounts, Joint Tenancy accounts, trust accounts and Transfer on Death accounts, as well as shares purchased by a trust of which the investor is a beneficiary. For purposes of the Letter of Intent and right of accumulation, the investor may not combine with the investor’s other holdings shares held in pension, profit sharing or other employer-sponsored retirement plans if those shares are held in the name of a nominee or custodian.

In order to receive a reduced sales charge, at the time an investor purchases shares of the Fund, the investor should inform the Financial Intermediary and/or BlackRock Funds of any other shares of the Fund or any other BlackRock Fund or Eligible Unlisted BlackRock Closed-End Fund that qualify for a reduced sales charge. Failure by the investor to notify the Financial Intermediary or BlackRock Funds may result in the investor not receiving the sales charge reduction to which the investor is otherwise entitled.

The Financial Intermediary or BlackRock Funds may request documentation — including account statements and records of the original cost of the shares owned by the investor, the investor’s spouse and/or children showing that the investor qualifies for a reduced sales charge. The investor should retain these records because — depending on where an account is held or the type of account — the Fund and/or the Financial Intermediary, BlackRock Funds or Eligible Unlisted BlackRock Closed-End Funds may not be able to maintain this information.

For more information, see the SAI or contact your Financial Intermediary.

Letter of Intent

An investor may qualify for a reduced front-end sales charge immediately by signing a “Letter of Intent” stating the investor’s intention to make one or more of the following investments within the next 13 months which would, if bought all at once, qualify the investor for a reduced sales charge:

i.	Buy a specified amount of Investor A, Investor C, Investor P, Institutional, Class K and/or Premier Shares,
ii.	Make an investment in one or more Eligible Unlisted BlackRock Closed-End Funds and/or
iii.	Make an investment through the BlackRock CollegeAdvantage 529 Program in one or more BlackRock Funds.

The initial investment must meet the minimum initial purchase requirement. The 13-month Letter of Intent period commences on the day that the Letter of Intent is received by the Fund.

The market value of current holdings in the BlackRock Funds (including Investor A, Investor C, Investor P, Institutional, Class K and Premier Shares, Eligible Unlisted BlackRock Closed-End Funds and the BlackRock CollegeAdvantage 529 Program Class A and Class C Units) as of the date of commencement that are eligible under the Right of Accumulation may be counted towards the sales charge reduction.

The investor must notify the Fund of (i) any current holdings in the BlackRock Funds, Eligible Unlisted BlackRock Closed-End Funds and/or the BlackRock CollegeAdvantage 529 Program that should be counted towards the sales charge reduction and (ii) any subsequent purchases that should be counted towards the Letter of Intent.

During the term of the Letter of Intent, the Fund will hold Investor A Shares representing up to 5% of the indicated amount in an escrow account for payment of a higher sales load if the full amount indicated in the Letter of Intent is not purchased. If the full amount indicated is not purchased within the 13-month period, and the investor does not pay the higher sales load within 20 days, the Fund will redeem enough of the Investor A Shares held in escrow to pay the difference.

Right of Accumulation

Investors have a “right of accumulation” under which any of the following may be combined with the amount of the current purchase in determining whether an investor qualifies for a breakpoint and a reduced front-end sales charge:

i.	The current value of an investor’s existing Investor A and A1, Investor C, C1, C2 and C3, Investor P, Institutional, Class K and Premier Shares in most BlackRock Funds,
ii.	The current value of an investor’s existing shares of Eligible Unlisted BlackRock Closed-End Funds and
iii.	The investment in the BlackRock CollegeAdvantage 529 Program by the investor or by or on behalf of the investor’s spouse and children.

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Intermediary will be treated similarly. In order to use this right, the investor must alert BlackRock to the existence of any previously purchased shares.

Other Front-End Sales Charge Waivers

The following persons may also buy Investor A Shares without paying a sales charge:

■	Certain employer-sponsored retirement plans. For purposes of this waiver, employer-sponsored retirement plans do not include SEP IRAs, SIMPLE IRAs or SARSEPs;
■	Rollovers of current investments through certain employer-sponsored retirement plans, provided the shares are transferred to the same BlackRock Fund as either a direct rollover, or subsequent to distribution, the rolled-over proceeds are contributed to a BlackRock IRA through an account directly with the Fund; or purchases by IRA programs that are sponsored by Financial Intermediary firms provided the Financial Intermediary firm has entered into a Class A Net Asset Value agreement with respect to such program with the Distributor;
■	Insurance company separate accounts;
■	Registered investment advisers, trust companies and bank trust departments exercising discretionary investment authority with respect to amounts to be invested in the Fund;
■	Persons participating in a fee-based program (such as a wrap account) under which they pay advisory fees to a broker-dealer or other financial institution;
■	Financial Intermediaries who have entered into an agreement with the Distributor and have been approved by the Distributor to offer Fund shares to self-directed investment brokerage accounts that may or may not charge a transaction fee;
■	Persons associated with the Fund, the Fund’s manager, the Fund’s sub-adviser, transfer agent, Distributor, fund accounting agents, Barclays PLC (“Barclays”) and their respective affiliates (to the extent permitted by these firms) including: (a) officers, directors and partners; (b) employees and retirees; (c) employees of firms who have entered into selling agreements to distribute shares of BlackRock Funds; (d) immediate family members of such persons; and (e) any trust, pension, profit-sharing or other benefit plan for any of the persons set forth in (a) through (d); and
■	State sponsored 529 college savings plans.

In addition, a sales charge waiver may be available for investors exchanging Investor P Shares of another BlackRock Fund for Investor A Shares of the Fund through an intermediary-processed exchange, provided that the investor had previously paid a sales charge with respect to such shares.

In addition, Financial Intermediaries may, in connection with a change in account type or otherwise in accordance with a Financial Intermediary’s policies and procedures, exchange one class of shares for Investor A Shares of the same Fund. In such cases, such exchange would not be subject to an Investor A Shares sales charge. The availability of Investor A Shares sales charge waivers may depend on the policies, procedures and trading platforms of your Financial Intermediary; consult your financial adviser.

See the “Intermediary-Defined Sales Charge Waiver Policies” section for sales charge reductions and waivers that may be available to customers of certain Financial Intermediaries.

Investor A Shares at Net Asset Value

If you invest $250,000 or more (for the High Yield Fund and the National Fund) or $100,000 or more (for the Short-Term Fund), you will not pay any initial sales charge. However, if you redeem your Investor A Shares within 18 months (for the High Yield Fund and the National Fund) or 9 months (for the Short-Term Fund) after purchase, you may be charged a deferred sales charge of 1.00% (for the High Yield Fund and the National Fund) or 0.25% (for the Short-Term Fund) of the lesser of the original cost of the shares being redeemed or your redemption proceeds. For a discussion on waivers, see “Contingent Deferred Sales Charge Waivers.”

If you are eligible to buy both Investor A and Institutional Shares, you should buy Institutional Shares since Investor A Shares are subject to a front end sales charge and an annual 0.25% service fee, while Institutional Shares are not. The Distributor normally pays the annual Investor A Shares service fee to dealers as a shareholder servicing fee on a monthly basis.

Investor C Shares — Deferred Sales Charge Option

If you select Investor C Shares, you do not pay an initial sales charge at the time of purchase. However, if you redeem your Investor C Shares within one year after purchase, you may be required to pay a deferred sales charge of 1.00%. The charge will apply to the lesser of the original cost of the shares being redeemed or the proceeds of your redemption. When you redeem Investor C Shares, the redemption order is processed so that the lowest deferred sales charge is charged. Investor C Shares that are not subject to the deferred sales charge are redeemed first. In addition, you will not be charged a deferred sales charge when you redeem shares that you acquire through reinvestment of

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Fund dividends or capital gains. Any CDSC paid on the redemptions of Investor C Shares expressed as a percentage of the applicable redemption amount may be higher or lower than the charge described due to rounding.

Effective November 8, 2018 (the “Effective Date”), Investor C Shares will automatically convert to Investor A Shares approximately ten years after the date of purchase. It is the Financial Intermediary’s responsibility to ensure that the shareholder is credited with the proper holding period. As of the Effective Date, certain Financial Intermediaries, including group retirement recordkeeping platforms, may not have been tracking such holding periods and therefore may not be able to process such conversions. In such instances, the automatic conversion of Investor C Shares to Investor A Shares will occur ten years after the Effective Date. The automatic conversion of Investor C Shares to Investor A Shares is not a taxable event for Federal income tax purposes. Please consult your Financial Intermediary for additional information.

See the “Intermediary-Defined Sales Charge Waiver Policies” section for sales charge reductions and waivers that may be available to customers of certain Financial Intermediaries.

You will also pay distribution fees of 0.75% and service fees of 0.25% for Investor C Shares each year. Because these fees are paid out of each Fund’s assets on an ongoing basis, over time these fees increase the cost of your investment and may cost you more than paying other types of sales charges. The Distributor uses the money that it receives from the deferred sales charges and the distribution fees to cover the costs of marketing, advertising and compensating the Financial Intermediary who assists you in purchasing Fund shares.

The Distributor currently pays dealers a sales concession of 1.00% of the purchase price of Investor C Shares from its own resources at the time of sale. The Distributor pays the annual Investor C Shares distribution fee and the annual Investor C Shares service fee as an ongoing concession and as a shareholder servicing fee, respectively, to dealers for Investor C Shares held for over a year and normally retains the Investor C Shares distribution fee and service fee during the first year after purchase. For certain employer-sponsored retirement plans, the Distributor will pay the full Investor C Shares distribution fee and service fee to dealers beginning in the first year after purchase in lieu of paying the sales concession. This may depend on the policies, procedures and trading platforms of your Financial Intermediary; consult your financial adviser.

Contingent Deferred Sales Charge Waivers

The deferred sales charge relating to Investor A and Investor C Shares may be reduced or waived in certain circumstances, such as:

■	Redemptions of shares purchased through certain employer-sponsored retirement plans and rollovers of current investments in a Fund through such plans;
■	Exchanges pursuant to the exchange privilege, as described in “How to Buy, Sell, Exchange and Transfer Shares — How to Exchange Shares or Transfer Your Account”;
■	Redemptions made in connection with minimum required distributions from IRA or 403(b)(7) accounts due to the shareholder reaching the age of 70½;
■	Certain post-retirement withdrawals from an IRA or other retirement plan if you are over 59½ years old and you purchased your shares prior to October 2, 2006;
■	Redemptions made with respect to certain retirement plans sponsored by a Fund, BlackRock or an affiliate;
■	Redemptions resulting from shareholder death as long as the waiver request is made within one year of death or, if later, reasonably promptly following completion of probate (including in connection with the distribution of account assets to a beneficiary of the decedent);
■	Withdrawals resulting from shareholder disability (as defined in the Internal Revenue Code) as long as the disability arose subsequent to the purchase of the shares;
■	Involuntary redemptions made of shares in accounts with low balances;

■	Certain redemptions made through the Systematic Withdrawal Plan (“SWP”) offered by a Fund, BlackRock or an affiliate;

■	Redemptions related to the payment of BNY Mellon Investment Servicing Trust Company custodial IRA fees; and
■	Redemptions when a shareholder can demonstrate hardship, in the absolute discretion of a Fund.

See the “Intermediary-Defined Sales Charge Waiver Policies” section for sales charge reductions and waivers that may be available to customers of certain Financial Intermediaries.

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Institutional Shares

Institutional Shares are not subject to any sales charge. Only certain investors are eligible to buy Institutional Shares. Your Financial Intermediary can help you determine whether you are eligible to buy Institutional Shares. The Fund may permit a lower initial investment for certain investors if their purchase, combined with purchases by other investors received together by the Fund, meets the minimum investment requirement.

Institutional Shares may also be available on certain brokerage platforms. An investor transacting in Institutional Shares on such brokerage platforms through a broker acting as an agent for the investor may be required to pay a commission and/or other forms of compensation to the broker. Shares of the Fund are available in other share classes that have different fees and expenses.

Eligible Institutional Share investors include the following:

■	Individuals and “Institutional Investors” with a minimum initial investment of $2 million who may purchase shares of a Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares;
■	Clients of Financial Intermediaries that: (i) charge such clients a fee for advisory, investment consulting, or similar services or (ii) have entered into an agreement with the Distributor to offer Institutional Shares through a no-load program or investment platform, in each case, with no minimum initial investment;
■	Clients investing through Financial Intermediaries that have entered into an agreement with the Distributor to offer such shares on a platform that charges a transaction based sales commission outside of the Fund, with a minimum initial investment of $1,000;
■	Employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs or SARSEPs), state sponsored 529 college savings plans, collective trust funds, investment companies or other pooled investment vehicles, unaffiliated thrifts and unaffiliated banks and trust companies, each of which is not subject to any minimum initial investment and may purchase shares of a Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares;

■

Trust department clients of PNC Bank, National Association and Bank of America, N.A. and their affiliates for whom they (i) act in a fiduciary capacity (excluding participant directed employee benefit plans); (ii) otherwise have investment discretion; or (iii) act as custodian for at least $2 million in assets, who are not subject to any minimum initial investment;

■	Holders of certain Bank of America Corporation (“BofA Corp.”) sponsored unit investment trusts (“UITs”) who reinvest dividends received from such UITs in shares of the Fund, who are not subject to any minimum initial investment;

■

Employees, officers and directors/trustees of BlackRock, Inc., BlackRock Funds, BofA Corp., The PNC Financial Services Group, Inc., Barclays or their respective affiliates and immediate family members of such persons, if they open an account directly with BlackRock, who are not subject to any minimum initial investment; and

■	Tax-qualified accounts for insurance agents that are registered representatives of an insurance company’s broker-dealer that has entered into an agreement with the Distributor to offer Institutional Shares, and the family members of such persons.

The Fund reserves the right to modify or waive the above-stated policies at any time.

Distribution and Shareholder Servicing Payments

Plan Payments

BlackRock Municipal Bond Fund, Inc. (the “Corporation”), on behalf of the Funds, has adopted a plan (the “Plan”) pursuant to Rule 12b-1 under the Investment Company Act with respect to the Investor Shares that allows a Fund to pay distribution fees for the sale of its shares and/or shareholder servicing fees for certain services provided to its shareholders.

Under the Plan, Investor C Shares pay a distribution fee to the Distributor and/or its affiliates for distribution and sales support services. The distribution fees may be used to pay the Distributor for distribution and sales support services and to pay the Distributor and BlackRock and its affiliates for sales support services provided and related expenses incurred in connection with the sale of Investor C Shares. The distribution fees may also be used to pay Financial Intermediaries for sales support services and related expenses. All Investor C Shares pay a maximum distribution fee per year that is a percentage of the average daily net asset value of the Investor C Shares. Institutional and Investor A Shares do not pay distribution fees.

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Under the Plan, a Fund also pays shareholder servicing fees (also referred to as general shareholder liaison services fees) to Financial Intermediaries for providing support services to their customers who own Investor Shares of the Fund. The shareholder servicing fee payment is calculated as a percentage of the average daily net asset value of Investor Shares of the Funds. All Investor Shares pay this shareholder servicing fee. Institutional Shares do not pay a shareholder servicing fee.

In return for the shareholder servicing fee, Financial Intermediaries (including BlackRock) may provide one or more of the following services to their customers who own Investor Shares:

■	Answering customer inquiries regarding account status and history, the manner in which purchases, exchanges and redemptions or repurchases of shares may be effected and certain other matters pertaining to the customers’ investments;
■	Assisting customers in designating and changing dividend options, account designations and addresses; and
■	Providing other similar shareholder liaison services.

Because the fees paid by a Fund under the Plan are paid out of Fund assets on an ongoing basis, over time these fees will increase the cost of your investment and may cost you more than paying other types of sales charges. In addition, the distribution fees paid by Investor C Shares may over time cost investors more than the front-end sales charge on Investor A Shares. For more information on the Plan, including a complete list of services provided thereunder, see the SAI.

Other Payments by the Fund

In addition to fees that a Fund may pay to a Financial Intermediary pursuant to the Plan and fees a Fund pays to its transfer agent, BNY Mellon Investment Servicing (US) Inc. (the “Transfer Agent”), BlackRock, on behalf of a Fund, may enter into non-Plan agreements with affiliated and unaffiliated Financial Intermediaries pursuant to which the Fund will pay a Financial Intermediary for administrative, networking, recordkeeping, sub-transfer agency, sub-accounting and/or shareholder services. These non-Plan payments are generally based on either (1) a percentage of the average daily net assets of Fund shareholders serviced by a Financial Intermediary or (2) a fixed dollar amount for each account serviced by a Financial Intermediary. The aggregate amount of these payments may be substantial.

Other Payments by BlackRock

From time to time, BlackRock, the Distributor or their affiliates also may pay a portion of the fees for administrative, networking, recordkeeping, sub-transfer agency, sub-accounting and shareholder services described above at its or their own expense and out of its or their profits. BlackRock, the Distributor and their affiliates may also compensate affiliated and unaffiliated Financial Intermediaries for the sale and distribution of shares of the Funds. These payments would be in addition to the Fund payments described in this prospectus and may be a fixed dollar amount, may be based on the number of customer accounts maintained by the Financial Intermediary, may be based on a percentage of the value of shares sold to, or held by, customers of the Financial Intermediary or may be calculated on another basis. The aggregate amount of these payments by BlackRock, the Distributor and their affiliates may be substantial and, in some circumstances, may create an incentive for a Financial Intermediary, its employees or associated persons to recommend or sell shares of a Fund to you.

Please contact your Financial Intermediary for details about payments it may receive from a Fund or from BlackRock, the Distributor or their affiliates. For more information, see the SAI.

How to Buy, Sell, Exchange and Transfer Shares

The chart on the following pages summarizes how to buy, sell, exchange and transfer shares through your Financial Intermediary. You may also buy, sell, exchange and transfer shares through BlackRock if your account is held directly with BlackRock. To learn more about buying, selling, exchanging or transferring shares through BlackRock, call (800) 441-7762. Because the selection of a mutual fund involves many considerations, your Financial Intermediary may help you with this decision.

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taxpayer identification number, and (ii) a Financial Intermediary or a shareholder that is an entity be domiciled in the United States and have a valid U.S. taxpayer identification number or be domiciled in a U.S. territory and have a valid U.S. taxpayer identification number or IRS Form W-8. Any existing account that is updated to reflect a non-U.S. address will also be restricted from making additional investments.

Each Fund may reject any purchase order, modify or waive the minimum initial or subsequent investment requirements for any shareholders and suspend and resume the sale of any share class of the Fund at any time for any reason. In addition, the Funds may waive certain requirements regarding the purchase, sale, exchange or transfer of shares described below.

Under certain circumstances, if no activity occurs in an account within a time period specified by state law, a shareholder’s shares in a Fund may be transferred to that state.

How to Buy Shares

	Your Choices	Important Information for You to Know
Initial Purchase	First, select the share class appropriate for you	Refer to the “Share Classes at a Glance” table in this prospectus (be sure to read this prospectus carefully). When you place your initial order, you must indicate which share class you select (if you do not specify a share class and do not qualify to purchase Institutional Shares, you will receive Investor A Shares). Certain factors, such as the amount of your investment, your time frame for investing and your financial goals, may affect which share class you choose. Your Financial Intermediary can help you determine which share class is appropriate for you.
	Next, determine the amount of your investment	Refer to the minimum initial investment in the “Share Classes at a Glance” table of this prospectus. Be sure to note the maximum investment amounts in Investor C Shares. See “Account Information — Details About the Share Classes” for information on a lower initial investment requirement for certain Fund investors if their purchase, combined with purchases by other investors received together by the Fund, meets the minimum investment requirement.
	Have your Financial Intermediary submit your purchase order	The price of your shares is based on the next calculation of the Fund’s net asset value after your order is placed. Any purchase orders placed prior to the close of business on the New York Stock Exchange (the “NYSE”) (generally 4:00 p.m. Eastern time) will be priced at the net asset value determined that day. Certain Financial Intermediaries, however, may require submission of orders prior to that time. Purchase orders placed after that time will be priced at the net asset value determined on the next business day. A broker-dealer or financial institution maintaining the account in which you hold shares may charge a separate account, service or transaction fee on the purchase or sale of Fund shares that would be in addition to the fees and expenses shown in the Fund’s “Fees and Expenses” table. The Fund may reject any order to buy shares and may suspend the sale of shares at any time. Certain Financial Intermediaries may charge a processing fee to confirm a purchase.
	Or contact BlackRock (for accounts held directly with BlackRock)	To purchase shares directly from BlackRock, call (800) 441-7762 and request a new account application. Mail the completed application along with a check payable to “BlackRock Funds” to the Transfer Agent at the address on the application.
Add to Your Investment	Purchase additional shares	For Investor A and Investor C Shares, the minimum investment for additional purchases is generally $50 for all accounts (with the exception of certain employer-sponsored retirement plans which may have a lower minimum for additional purchases). The minimums for additional purchases may be waived under certain circumstances. Institutional Shares have no minimum for additional purchases.
	Have your Financial Intermediary submit your purchase order for additional shares	To purchase additional shares you may contact your Financial Intermediary. For more details on purchasing by Internet see below.

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	Your Choices	Important Information for You to Know
Add to Your Investment (continued)	Or contact BlackRock (for accounts held directly with BlackRock)	Purchase by Telephone: Call (800) 441-7762 and speak with one of our representatives. The Fund has the right to reject any telephone request for any reason. Purchase in Writing: You may send a written request to BlackRock at the address on the back cover of this prospectus. Purchase by VRU: Investor Shares may also be purchased by use of the Fund’s automated voice response unit (“VRU”) service at (800) 441-7762. Purchase by Internet: You may purchase your shares and view activity in your account by logging onto the BlackRock website at www.blackrock.com. Purchases made on the Internet using the Automated Clearing House (“ACH”) will have a trade date that is the day after the purchase is made. Certain institutional clients’ purchase orders of Institutional Shares placed by wire prior to the close of business on the NYSE will be priced at the net asset value determined that day. Contact your Financial Intermediary or BlackRock for further information. The Fund limits Internet purchases in shares of the Fund to $25,000 per trade. Different maximums may apply to certain institutional investors. Please read the On-Line Services Disclosure Statement and User Agreement, the Terms and Conditions page and the Consent to Electronic Delivery Agreement (if you consent to electronic delivery), before attempting to transact online. The Fund employs reasonable procedures to confirm that transactions entered over the Internet are genuine. By entering into the User Agreement with the Fund in order to open an account through the website, the shareholder waives any right to reclaim any losses from the Fund or any of its affiliates incurred through fraudulent activity.
	Acquire additional shares by reinvesting dividends and capital gains	All dividends and capital gains distributions are automatically reinvested without a sales charge. To make any changes to your dividend and/or capital gains distributions options, please call (800) 441-7762 or contact your Financial Intermediary (if your account is not held directly with BlackRock).
	Participate in the AIP	BlackRock’s AIP allows you to invest a specific amount on a periodic basis from your checking or savings account into your investment account. Refer to the “Account Services and Privileges” section of this prospectus for additional information.
How to Pay for Shares	Making payment for purchases	Payment for an order must be made in Federal funds or other immediately available funds by the time specified by your Financial Intermediary, but in no event later than 4:00 p.m. (Eastern time) on the second business day (in the case of Investor Shares) or the first business day (in the case of Institutional Shares) following BlackRock’s receipt of the order. If payment is not received by this time, the order will be canceled and you and your Financial Intermediary will be responsible for any loss to the Fund. For shares purchased directly from the Fund, a check payable to BlackRock Funds which bears the name of the Fund must accompany a completed purchase application. There is a $20 fee for each purchase check that is returned due to insufficient funds. The Fund does not accept third-party checks. You may also wire Federal funds to the Fund to purchase shares, but you must call (800) 441-7762 before doing so to confirm the wiring instructions.

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How to Sell Shares

	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares	Have your Financial Intermediary submit your sales order	You can make redemption requests through your Financial Intermediary. Shareholders should indicate whether they are redeeming Investor A, Investor C or Institutional Shares. The price of your shares is based on the next calculation of the Fund’s net asset value after your order is placed. For your redemption request to be priced at the net asset value on the day of your request, you must submit your request to your Financial Intermediary prior to that day’s close of business on the NYSE (generally 4:00 p.m. Eastern time). Certain Financial Intermediaries, however, may require submission of orders prior to that time. Any redemption request placed after that time will be priced at the net asset value at the close of business on the next business day. Regardless of the method the Fund uses to make payment of your redemption proceeds (check, wire or ACH), your redemption proceeds typically will be sent one to two business days after your request is submitted, but in any event, within seven days. Certain Financial Intermediaries may charge a fee to process a redemption of shares. The Fund may reject an order to sell shares under certain circumstances.
	Selling shares held directly with BlackRock	Methods of Redeeming Redeem by Telephone: You may redeem Investor Shares held directly with BlackRock by telephone request if certain conditions are met and if the amount being sold is less than (i) $100,000 for payments by check or (ii) $250,000 for payments through ACH or wire transfer. Certain redemption requests, such as those in excess of these amounts, must be in writing with a medallion signature guarantee. For Institutional Shares, certain redemption requests may require written instructions with a medallion signature guarantee. Call (800) 441-7762 for details. You can obtain a medallion signature guarantee stamp from a bank, securities dealer, securities broker, credit union, savings and loan association, national securities exchange or registered securities association. A notary public seal will not be acceptable. The Fund, its administrators and the Distributor will employ reasonable procedures to confirm that instructions communicated by telephone are genuine. The Fund and its service providers will not be liable for any loss, liability, cost or expense for acting upon telephone instructions that are reasonably believed to be genuine in accordance with such procedures. The Fund may refuse a telephone redemption request if it believes it is advisable to do so. During periods of substantial economic or market change, telephone redemptions may be difficult to complete. Please find alternative redemption methods below. Redeem by VRU: Investor Shares may also be redeemed by use of the Fund’s automated VRU service. Payment for Investor Shares redeemed by the VRU service may be made for non-retirement accounts in amounts up to $25,000, either through check, ACH or wire. Redeem by Internet: You may redeem in your account, by logging onto the BlackRock website at www.blackrock.com. Proceeds from Internet redemptions may be sent via check, ACH or wire to the bank account of record. Payment for Investor Shares redeemed by Internet may be made for non-retirement accounts in amounts up to $25,000, either through check, ACH or wire. Different maximums may apply to investors in Institutional Shares. Redeem in Writing: You may sell shares held at BlackRock by writing to BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019 or for overnight delivery, 4400 Computer Drive, Westborough, Massachusetts 01581. All shareholders on the account must sign the letter. A medallion signature guarantee will generally be required but

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Selling shares held directly with BlackRock (continued)	may be waived in certain limited circumstances. You can obtain a medallion signature guarantee stamp from a bank, securities dealer, securities broker, credit union, savings and loan association, national securities exchange or registered securities association. A notary public seal will not be acceptable. If you hold stock certificates, return the certificates with the letter. Proceeds from redemptions may be sent via check, ACH or wire to the bank account of record. Payment of Redemption Proceeds Redemption proceeds may be paid by check or, if the Fund has verified banking information on file, through ACH or by wire transfer. Payment by Check: BlackRock will normally mail redemption proceeds within three business days following receipt of a properly completed request, but in any event within seven days. Shares can be redeemed by telephone and the proceeds sent by check to the shareholder at the address on record. Shareholders will pay $15 for redemption proceeds sent by check via overnight mail. You are responsible for any additional charges imposed by your bank for this service. Each Fund reserves the right to reinvest any dividend or distribution amounts (e.g., income dividends or capital gains) which you have elected to receive by check should your check be returned as undeliverable or remain uncashed for more than 6 months. No interest will accrue on amounts represented by uncashed checks. Your check will be reinvested in your account at the net asset value next calculated, on the day of the investment. When reinvested, those amounts are subject to the risk of loss like any fund investment. If you elect to receive distributions in cash and a check remains undeliverable or uncashed for more than 6 months, your cash election may also be changed automatically to reinvest and your future dividend and capital gains distributions will be reinvested in the Fund at the net asset value as of the date of payment of the distribution. Payment by Wire Transfer: Payment for redeemed shares for which a redemption order is received before 4:00 p.m. (Eastern time) on a business day is normally made in Federal funds wired to the redeeming shareholder on the next business day, provided that the Fund’s custodian is also open for business. Payment for redemption orders received after 4:00 p.m. (Eastern time) or on a day when the Fund’s custodian is closed is normally wired in Federal funds on the next business day following redemption on which the Fund’s custodian is open for business. The Fund reserves the right to wire redemption proceeds within seven days after receiving a redemption order if, in the judgment of the Fund, an earlier payment could adversely affect the Fund. If a shareholder has given authorization for expedited redemption, shares can be redeemed by Federal wire transfer to a single previously designated bank account. Shareholders will pay $7.50 for redemption proceeds sent by Federal wire transfer. You are responsible for any additional charges imposed by your bank for this service. No charge for wiring redemption payments with respect to Institutional Shares is imposed by the Fund. The Fund is not responsible for the efficiency of the Federal wire system or the shareholder’s firm or bank. To change the name of the single, designated bank account to receive wire redemption proceeds, it is necessary to send a written request to the Fund at the address on the back cover of this prospectus. Payment by ACH: Redemption proceeds may be sent to the shareholder’s bank account (checking or savings) via ACH. Payment for redeemed shares for which a redemption order is received before 4:00 p.m. (Eastern time) on a business day is normally sent to the redeeming shareholder the next business day, with receipt at the receiving bank within the next two business days (48-72 hours); provided that the Fund’s custodian is also open for business. Payment for redemption orders received after 4:00 p.m. (Eastern time) or on a

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Selling shares held directly with BlackRock (continued)	day when the Fund’s custodian is closed is normally sent on the next business day following redemption on which the Fund’s custodian is open for business. The Fund reserves the right to send redemption proceeds within seven days after receiving a redemption order if, in the judgment of the Fund, an earlier payment could adversely affect the Fund. No charge for sending redemption payments via ACH is imposed by the Fund. *** If you make a redemption request before the Fund has collected payment for the purchase of shares, the Fund may delay mailing your proceeds. This delay will usually not exceed ten days.
Redemption Proceeds		Under normal circumstances, the Fund expects to meet redemption requests by using cash or cash equivalents in its portfolio or by selling portfolio assets to generate cash. During periods of stressed market conditions, when a significant portion of the Fund’s portfolio may be comprised of less-liquid investments, the Fund may be more likely to limit cash redemptions and may determine to pay redemption proceeds by (i) borrowing under a line of credit it has entered into with a group of lenders, (ii) borrowing from another BlackRock Fund pursuant to an interfund lending program, to the extent permitted by the Fund’s investment policies and restrictions as set forth in the SAI, and/or (iii) transferring portfolio securities in-kind to you. The SAI includes more information about the Fund’s line of credit and interfund lending program, to the extent applicable. If the Fund pays redemption proceeds by transferring portfolio securities in-kind to you, you may pay transaction costs to dispose of the securities, and you may receive less for them than the price at which they were valued for purposes of redemption.

How to Exchange Shares or Transfer Your Account

	Your Choices	Important Information for You to Know
Exchange Privilege	Selling shares of one BlackRock Fund to purchase shares of another BlackRock Fund (“exchanging”)	Investor or Institutional Shares of the Fund are generally exchangeable for shares of the same class of another BlackRock Fund, to the extent such shares are offered by your Financial Intermediary. You can exchange $1,000 or more of Investor A or Investor C Shares from one fund into the same class of another fund which offers that same class of shares (you can exchange less than $1,000 of Investor A or Investor C Shares if you already have an account in the fund into which you are exchanging). Investors who currently own Institutional Shares of the Fund may make exchanges into Institutional Shares of other BlackRock Funds except for investors holding shares through certain client accounts at Financial Intermediaries that are omnibus with the Fund and do not meet applicable minimums. There is no required minimum amount with respect to exchanges of Institutional Shares. You may only exchange into a share class and fund that are open to new investors or in which you have a current account if the fund is closed to new investors. Some of the BlackRock Funds impose a different initial or deferred sales charge schedule. The CDSC will continue to be measured from the date of the original purchase. The CDSC schedule applicable to your original purchase will apply to the shares you receive in the exchange and any subsequent exchange. To exercise the exchange privilege, you may contact your Financial Intermediary. Alternatively, if your account is held directly with BlackRock, you may: (i) call (800) 441-7762 and speak with one of our representatives, (ii) make the exchange via the Internet by accessing your account online at www.blackrock.com, or (iii) send a written request to the Fund at the address on the back cover of this prospectus. Please note, if you indicated on your new account

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	Your Choices	Important Information for You to Know
Exchange Privilege (continued)	Selling shares of one BlackRock Fund to purchase shares of another BlackRock Fund (“exchanging”) (continued)	application that you did not want the Telephone Exchange Privilege, you will not be able to place exchanges via the telephone until you update this option either in writing or by calling (800) 441-7762. The Fund has the right to reject any telephone request for any reason. Although there is currently no limit on the number of exchanges that you can make, the exchange privilege may be modified or terminated at any time in the future. The Fund may suspend or terminate your exchange privilege at any time for any reason, including if the Fund believes, in its sole discretion, that you are engaging in market timing activities. See “Short-Term Trading Policy” below. For U.S. federal income tax purposes a share exchange is a taxable event and a capital gain or loss may be realized. Please consult your tax adviser or other Financial Intermediary before making an exchange request.
Transfer Shares to Another Financial Intermediary	Transfer to a participating Financial Intermediary	You may transfer your shares of the Fund only to another Financial Intermediary that has entered into an agreement with the Distributor. Certain shareholder services may not be available for the transferred shares. All future trading of these assets must be coordinated by the receiving firm. If your account is held directly with BlackRock, you may call (800) 441-7762 with any questions; otherwise please contact your Financial Intermediary to accomplish the transfer of shares.
	Transfer to a non-participating Financial Intermediary	You must either: • Transfer your shares to an account with the Fund; or • Sell your shares, paying any applicable deferred sales charge. If your account is held directly with BlackRock, you may call (800) 441-7762 with any questions; otherwise please contact your Financial Intermediary to accomplish the transfer of shares.

Account Services and Privileges

The following table provides examples of account services and privileges available in your BlackRock account. Certain of these account services and privileges are only available to shareholders of Investor Shares whose accounts are held directly with BlackRock. If your account is held directly with BlackRock, please call (800) 441-7762 or visit www.blackrock.com for additional information as well as forms and applications. Otherwise, please contact your Financial Intermediary for assistance in requesting one or more of the following services and privileges.

Automatic Investment Plan	Allows systematic investments on a periodic basis from your checking or savings account.	BlackRock’s AIP allows you to invest a specific amount on a periodic basis from your checking or savings account into your investment account. You may apply for this option upon account opening or by completing the AIP application. The minimum investment amount for an automatic investment is $50 per portfolio.
Dividend Allocation Plan	Automatically invests your distributions into another BlackRock Fund of your choice pursuant to your instructions, without any fees or sales charges.	Dividend and capital gains distributions may be reinvested in your account to purchase additional shares or paid in cash. Using the Dividend Allocation Plan, you can direct your distributions to your bank account (checking or savings), to purchase shares of another fund at BlackRock without any fees or sales charges, or by check to a special payee. Please call (800) 441-7762 for details. If investing in another fund at BlackRock, the receiving fund must be open to new purchases.
EZ Trader	Allows an investor to purchase or sell Investor Shares by telephone or over the Internet through ACH.	(NOTE: This option is offered to shareholders whose accounts are held directly with BlackRock. Please speak with your Financial Intermediary if your account is held elsewhere.) Prior to establishing an EZ Trader account, please contact your bank to confirm that it is a member of the ACH system. Once confirmed, complete an application, making sure to include the appropriate bank information, and return the application to the address listed on the form. Prior to placing a telephone or Internet purchase or sale order, please call (800) 441-7762 to confirm that your bank information has been

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EZ Trader (continued)	Allows an investor to purchase or sell Investor Shares by telephone or over the Internet through ACH. (continued)	updated on your account. Once this is established, you may place your request to sell shares with the Fund by telephone or Internet. Proceeds will be sent to your pre-designated bank account.
Systematic Exchange Plan	This feature can be used by investors to systematically exchange money from one fund to up to four other funds.	A minimum of $10,000 in the initial BlackRock Fund is required, and investments in any additional funds must meet minimum initial investment requirements.
Systematic Withdrawal Plan	This feature can be used by investors who want to receive regular distributions from their accounts.	To start an SWP, a shareholder must have a current investment of $10,000 or more in a BlackRock Fund. Shareholders can elect to receive cash payments of $50 or more at any interval they choose. Shareholders may sign up by completing the SWP Application Form, which may be obtained from BlackRock. Shareholders should realize that if withdrawals exceed income the invested principal in their account will be depleted. To participate in the SWP, shareholders must have their dividends reinvested. Shareholders may change or cancel the SWP at any time, with a minimum of 24 hours’ notice. If a shareholder purchases additional Investor A Shares of a fund at the same time he or she redeems shares through the SWP, that investor may lose money because of the sales charge involved. No CDSC will be assessed on redemptions of Investor A or Investor C Shares made through the SWP that do not exceed 12% of the account’s net asset value on an annualized basis. For example, monthly, quarterly, and semi-annual SWP redemptions of Investor A or Investor C Shares will not be subject to the CDSC if they do not exceed 1%, 3% and 6%, respectively, of an account’s net asset value on the redemption date. SWP redemptions of Investor A or Investor C Shares in excess of this limit will still pay any applicable CDSC. Ask your Financial Intermediary for details.
Reinstatement Privilege		If you redeem Investor A or Institutional Shares and buy new Investor A Shares of the same or another BlackRock Fund (equal to all or a portion of the redemption amount) within 90 days of such redemption, you will not pay a sales charge on the new purchase amount. This right may be exercised within 90 days of the redemption, provided that the Investor A Share class of that fund is currently open to new investors or the shareholder has a current account in that closed fund. Shares will be purchased at the net asset value calculated at the close of trading on the day the request is received. To exercise this privilege, the Fund must receive written notification from the shareholder of record or the Financial Intermediary of record, at the time of purchase. Investors should consult a tax adviser concerning the tax consequences of exercising this reinstatement privilege.

Funds’ Rights

Each Fund may:

■	Suspend the right of redemption if trading is halted or restricted on the NYSE or under other emergency conditions described in the Investment Company Act;
■	Postpone the date of payment upon redemption if trading is halted or restricted on the NYSE or under other emergency conditions described in the Investment Company Act or if a redemption request is made before the Fund has collected payment for the purchase of shares;
■	Redeem shares for property other than cash as may be permitted under the Investment Company Act; and
■	Redeem shares involuntarily in certain cases, such as when the value of a shareholder account falls below a specified level.

Note on Low Balance Accounts. Because of the high cost of maintaining smaller shareholder accounts, BlackRock has set a minimum balance of $500 in each Fund position you hold within your account (“Fund Minimum”), and may redeem the shares in your account if the net asset value of those shares in your account falls below $500 for any reason, including market fluctuation.

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You will be notified that the value of your account is less than the Fund Minimum before the Fund makes any involuntary redemption. This notification will provide you with a 90 calendar day period to make an additional investment in order to bring the value of your account to at least $500 before the Fund makes an involuntary redemption. This involuntary redemption will not charge any deferred sales charge, and may not apply to accounts of certain employer-sponsored retirement plans (not including IRAs), qualified state tuition plan (529 Plan) accounts, and select fee-based programs at your Financial Intermediary.

Participation in Fee-Based Programs

If you participate in certain fee-based programs offered by BlackRock or an affiliate of BlackRock, or by Financial Intermediaries that have agreements with the Distributor or in certain fee-based programs in which BlackRock participates, you may be able to buy Institutional Shares, including by exchanges from other share classes. Sales charges on the shares being exchanged may be reduced or waived under certain circumstances. You generally cannot transfer shares held through a fee-based program into another account. Instead, if you choose to leave the fee-based program, you may have to redeem your shares held through the program and purchase shares of another class, which may be subject to distribution and service fees. This may be a taxable event and you may pay any applicable sales charges or redemption fees. Please speak to your Financial Intermediary for information about specific policies and procedures applicable to your account.

Generally, upon termination of a fee-based program, the shares may be liquidated or the shares can be held in an account. In certain instances, when a shareholder chooses to continue to hold the shares, whatever share class was held in the program can be held after termination. Shares that have been held for less than specified periods within the program may be subject to a fee upon redemption. Shareholders that held Investor A or Institutional Shares in the program may be eligible to purchase additional shares of the respective share class of the Fund, but may be subject to upfront sales charges with respect to Investor A Shares. Additional purchases of Institutional Shares are permitted only if you have an existing position at the time of purchase or are otherwise eligible to purchase Institutional Shares. Please speak to your Financial Intermediary for more information.

Certain Financial Intermediaries may, in connection with a change in account type (for example, due to leaving a fee-based program or upon termination of the fee-based program) or otherwise in accordance with the Financial Intermediary’s policies and procedures, exchange the share class held in the program for another share class of the same fund, provided that the exchanged shares are not subject to a sales charge and the shareholder meets the eligibility requirements of the new share class. Please speak to your Financial Intermediary for information about specific policies and procedures applicable to your account.

Details about the features of each fee-based program and the relevant charges, terms and conditions are included in the client agreement for each fee-based program and are available from your Financial Intermediary. Please speak to your Financial Intermediary for more information.

Short-Term Trading Policy

The Board of Directors (the “Board”) has determined that the interests of long-term shareholders and each Fund’s ability to manage its investments may be adversely affected when shares are repeatedly bought, sold or exchanged in response to short-term market fluctuations — also known as “market timing.” The Funds are not designed for market timing organizations or other entities using programmed or frequent purchases and sales or exchanges. The exchange privilege for Investor Shares and Institutional Shares is not intended as a vehicle for short-term trading. Excessive purchase and sale or exchange activity may interfere with portfolio management, increase expenses and taxes and may have an adverse effect on the performance of a Fund and its returns to shareholders. For example, large flows of cash into and out of a Fund may require the management team to allocate a significant amount of assets to cash or other short-term investments or sell securities, rather than maintaining such assets in securities selected to achieve the Fund’s investment objective. Frequent trading may cause a Fund to sell securities at less favorable prices, and transaction costs, such as brokerage commissions, can reduce a Fund’s performance.

A fund’s investment in non-U.S. securities is subject to the risk that an investor may seek to take advantage of a delay between the change in value of the fund’s portfolio securities and the determination of the fund’s net asset value as a result of different closing times of U.S. and non-U.S. markets by buying or selling fund shares at a price that does not reflect their true value. A similar risk exists for funds that invest in securities of small capitalization companies, securities of issuers located in emerging markets or high yield securities (junk bonds) that are thinly traded and therefore may have actual values that differ from their market prices. This short-term arbitrage activity can reduce the return received by long-term shareholders. The Funds will seek to eliminate these opportunities by using fair value pricing, as described in “Management of the Funds — Valuation of Fund Investments” below.

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Each Fund discourages market timing and seeks to prevent frequent purchases and sales or exchanges of Fund shares that it determines may be detrimental to the Fund or long-term shareholders. The Board has approved the policies discussed below to seek to deter market timing activity. The Board has not adopted any specific numerical restrictions on purchases, sales and exchanges of Fund shares because certain legitimate strategies will not result in harm to a Fund or its shareholders.

If as a result of its own investigation, information provided by a Financial Intermediary or other third party, or otherwise, a Fund believes, in its sole discretion, that your short-term trading is excessive or that you are engaging in market timing activity, it reserves the right to reject any specific purchase or exchange order. If a Fund rejects your purchase or exchange order, you will not be able to execute that transaction, and the Fund will not be responsible for any losses you therefore may suffer. For transactions placed directly with a Fund, the Fund may consider the trading history of accounts under common ownership or control for the purpose of enforcing these policies. Transactions placed through the same Financial Intermediary on an omnibus basis may be deemed part of a group for the purpose of this policy and may be rejected in whole or in part by a Fund. Certain accounts, such as omnibus accounts and accounts at Financial Intermediaries, however, include multiple investors and such accounts typically provide a Fund with net purchase or redemption and exchange requests on any given day where purchases, redemptions and exchanges of shares are netted against one another and the identity of individual purchasers, redeemers and exchangers whose orders are aggregated may not be known by the Fund. While a Fund monitors for market timing activity, a Fund may be unable to identify such activities because the netting effect in omnibus accounts often makes it more difficult to locate and eliminate market timers from the Funds. The Distributor has entered into agreements with respect to Financial Intermediaries that maintain omnibus accounts with the Transfer Agent pursuant to which such Financial Intermediaries undertake to cooperate with the Distributor in monitoring purchase, exchange and redemption orders by their customers in order to detect and prevent short-term or excessive trading in the Funds’ shares through such accounts. Identification of market timers may also be limited by operational systems and technical limitations. In the event that a Financial Intermediary is determined by a Fund to be engaged in market timing or other improper trading activity, the Funds’ Distributor may terminate such Financial Intermediary’s agreement with the Distributor, suspend such Financial Intermediary’s trading privileges or take other appropriate actions.

There is no assurance that the methods described above will prevent market timing or other trading that may be deemed abusive.

The Funds may from time to time use other methods that they believe are appropriate to deter market timing or other trading activity that may be detrimental to a Fund or long-term shareholders.

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Management of the Funds

BlackRock

BlackRock, each Fund’s investment adviser, manages each Fund’s investments and its business operations subject to the oversight of the Board of the Corporation. While BlackRock is ultimately responsible for the management of the Funds, it is able to draw upon the trading, research and expertise of its asset management affiliates for portfolio decisions and management with respect to certain portfolio securities. BlackRock is an indirect, wholly-owned subsidiary of BlackRock, Inc.

BlackRock, a registered investment adviser, was organized in 1994 to perform advisory services for investment companies. BlackRock and its affiliates had approximately $6.963 trillion in investment company and other portfolio assets under management as of September 30, 2019.

Each Fund has entered into a management agreement (each, a “Management Agreement”) with BlackRock. Under each Management Agreement, BlackRock receives for its services to each Fund a fee based on each Fund’s average daily net assets.

High Yield Fund Total Annual Management Fee (Before Waivers)

With respect to the High Yield Fund, the annual management fees payable to BlackRock (as a percentage of average daily net assets) are calculated as follows:

Average Daily Net Assets	Rate of Management Fee
Not exceeding $1 billion	0.47%
In excess of $1 billion but not exceeding $3 billion	0.44%
In excess of $3 billion but not exceeding $5 billion	0.42%
In excess of $5 billion but not exceeding $10 billion	0.41%
In excess of $10 billion	0.40%

National Fund and Short-Term Fund Total Annual Management Fees (Before Waivers)

With respect to the National Fund and the Short-Term Fund, the annual management fees payable to BlackRock (as a percentage of average daily net assets) are calculated as follows:

	Rate of Management Fee
Aggregate average daily net assets of the two combined Funds¹	National Fund	Short-Term Fund
First $250 million	0.410%	0.360%
$250 million – $400 million	0.385%	0.340%
$400 million – $550 million	0.385%	0.320%
Greater than $550 million	0.385%	0.290%

The reductions shall be applicable to each Fund regardless of size on a “uniform percentage” basis. Determination of the portion of the net assets of each Fund to which a reduced rate is applicable is made by multiplying the net assets of that Fund by “uniform percentages,” derived by dividing the amount by which the combined assets of both Funds exceed the various applicable breakpoints by such combined assets.

BlackRock has contractually agreed to waive the management fee with respect to any portion of each Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of a Fund.

BlackRock has voluntarily agreed to waive its management fees by the amount of advisory fees each Fund pays to BlackRock indirectly through its investment in affiliated money market funds (the “affiliated money market fund waiver”).

For the fiscal year ended June 30, 2019, the aggregate management fees, net of any applicable waivers, paid by each Fund to BlackRock as a percentage of each Fund’s average daily net assets were:

High Yield Fund

0.44%

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National Fund	0.36%
Short-Term Fund	0.23%

BlackRock has agreed to cap net expenses (excluding (i) interest, taxes, dividends tied to short sales, brokerage commissions, and other expenditures which are capitalized in accordance with generally accepted accounting principles; (ii) expenses incurred directly or indirectly by a Fund as a result of investments in other investment companies and pooled investment vehicles; (iii) other expenses attributable to, and incurred as a result of, a Fund’s investments; and (iv) extraordinary expenses (including litigation expenses) not incurred in the ordinary course of a Fund’s business, if any) of each share class of certain Funds at the levels shown below and in a Fund’s fees and expenses table in the “Fund Overview” section of this prospectus. Items (i), (ii), (iii) and (iv) in the preceding sentence are referred to in this prospectus as “Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses.” To achieve these expense caps, BlackRock has agreed to waive and/or reimburse fees or expenses if these operating expenses exceed a certain limit.

With respect to the Funds, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses to the amounts noted in the table below.

	Contractual Caps¹ on Total Annual Fund Operating Expenses² (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses)
High Yield Fund
Investor A Shares	0.79%
Investor C Shares	1.54%
Institutional Shares	0.54%
National Fund
Investor A Shares	0.68%
Investor C Shares	1.43%
Institutional Shares	0.43%
Short-Term Fund
Investor A Shares	0.61%
Investor C Shares	1.36%
Institutional Shares	0.36%

¹	The contractual caps are in effect through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of a Fund.

²	As a percentage of average daily net assets.

The amount of the contractual waivers and/or reimbursements of fees and expenses made pursuant to the contractual cap on net expenses will be reduced by the amount of the affiliated money market fund waiver.

As stated above, the waivers and reimbursements made pursuant to the contractual expense caps and described in the table above do not include Interest Expense. Each Fund’s Interest Expense is required to be reported as part of operating expenses in such Fund’s expense table for accounting purposes. Each Fund incurs Interest Expense when making certain investments (e.g., tender option bonds) to seek to enhance the yield and total return of the portfolio. The amount of Interest Expense (if any) will fluctuate with each Fund’s use of those investments.

A discussion of the basis for the Board’s approval of each Management Agreement with BlackRock is included in each Fund’s annual shareholder report for the fiscal year ended June 30, 2019.

From time to time, a manager, analyst, or other employee of BlackRock or its affiliates may express views regarding a particular asset class, company, security, industry, or market sector. The views expressed by any such person are the views of only that individual as of the time expressed and do not necessarily represent the views of BlackRock or any other person within the BlackRock organization. Any such views are subject to change at any time based upon market or other conditions and BlackRock disclaims any responsibility to update such views. These views may not be relied on as investment advice and, because investment decisions for the Funds are based on numerous factors, may not be relied on as an indication of trading intent on behalf of the Funds.

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July 25, 2018, the plaintiffs served a pleading that supplemented the time period of their alleged damages to run through the date of trial. The lawsuit seeks, among other things, to recover on behalf of Global Allocation and Equity Dividend all allegedly excessive advisory fees received by the Defendants beginning twelve months preceding the start of the lawsuit with respect to each of Global Allocation and Equity Dividend and ending on the date of judgment, along with purported lost investment returns on those amounts, plus interest. The Defendants believe the claims in the lawsuit are without merit. The trial on the remaining issues was completed on August 29, 2018. On February 8, 2019, the court issued an order dismissing the claims in their entirety. On March 8, 2019, the plaintiffs provided notice that they are appealing both the February 8, 2019 post-trial order and the June 13, 2018 order partially granting Defendants’ motion for summary judgment.

Portfolio Manager Information

Information regarding the portfolio managers of each Fund is set forth below. Further information regarding the portfolio managers, including other accounts managed, compensation, ownership of Fund shares, and possible conflicts of interest, is available in the Funds’ SAI.

High Yield Fund

The Fund is managed by a team of financial professionals. Walter O’Connor, CFA, and Theodore Jaeckel, CFA, are jointly and primarily responsible for the day-to-day management of the Fund.

Portfolio Manager	Primary Role	Since	Title and Recent Biography
Walter O’Connor, CFA	Responsible for the day-to-day management of each Fund’s portfolio, including setting each Fund’s overall investment strategy and overseeing the management of each Fund.	2006	Managing Director of BlackRock, Inc. since 2006.
Theodore R. Jaeckel, CFA	Responsible for the day-to-day management of each Fund’s portfolio, including setting each Fund’s overall investment strategy and overseeing the management of each Fund.	2006	Managing Director of BlackRock, Inc. since 2006.

National Fund

The Fund is managed by a team of financial professionals. Walter O’Connor, CFA, and Michael Kalinoski, CFA, are jointly and primarily responsible for the day-to-day management of the Fund.

Portfolio Manager	Primary Role	Since	Title and Recent Biography
Walter O’Connor, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	1996	Managing Director of BlackRock, Inc. since 2006.
Michael Kalinoski, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund..	2016	Director of BlackRock, Inc. since 2006.

Short-Term Fund

The Fund is managed by a team of financial professionals. Kevin Schiatta, CFA, and Kristi Manidis are jointly and primarily responsible for the day-to-day management of the Fund.

Portfolio Manager	Primary Role	Since	Title and Recent Biography
Kevin A. Schiatta, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	2016	Director of BlackRock, Inc. since 2006.
Kristi Manidis	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	2019	Director of BlackRock, Inc. since 2016; Vice President of BlackRock, Inc. from 2011 to 2015; Associate of BlackRock, Inc. from 2006 to 2010.

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Conflicts of Interest

The investment activities of BlackRock and its affiliates (including BlackRock, Inc. and its subsidiaries (collectively, the “Affiliates”)), The PNC Financial Services Group, Inc. (which, through a subsidiary, has a significant economic interest in BlackRock, Inc.) and its subsidiaries (each with The PNC Financial Services Group, Inc., an “Entity” and collectively, the “Entities”), and their respective directors, officers or employees, in the management of, or their interest in, their own accounts and other accounts they manage, may present conflicts of interest that could disadvantage the Funds and their shareholders.

BlackRock, its Affiliates and the Entities provide investment management services to other funds and discretionary managed accounts that may follow investment programs similar to that of the Funds. BlackRock, its Affiliates and the Entities are involved worldwide with a broad spectrum of financial services and asset management activities and may engage in the ordinary course of business in activities in which their interests or the interests of their clients may conflict with those of the Funds. BlackRock or one or more Affiliates or Entities act or may act as an investor, investment banker, research provider, investment manager, commodity pool operator, commodity trading advisor, financier, underwriter, adviser, market maker, trader, prime broker, lender, index provider, agent and/or principal, and have other direct and indirect interests in securities, currencies, commodities, derivatives and other instruments in which the Funds may directly or indirectly invest. Thus, it is likely that the Funds will have multiple business relationships with and will invest in, engage in transactions with, make voting decisions with respect to, or obtain services from, entities for which an Affiliate or an Entity performs or seeks to perform investment banking or other services. Specifically, the Funds may invest in securities of, or engage in other transactions with, companies with which an Affiliate or an Entity has developed or is trying to develop investment banking relationships or in which an Affiliate or an Entity has significant debt or equity investments or other interests. The Fund may also invest in issuances (such as structured notes) by entities for which an Affiliate or an Entity provides and is compensated for cash management services relating to the proceeds from the sale of such issuances. The Funds also may invest in securities of, or engage in other transactions with, companies for which an Affiliate or an Entity provides or may in the future provide research coverage. An Affiliate or Entity may have business relationships with, and purchase, or distribute or sell services or products from or to, distributors, consultants or others who recommend the Funds or who engage in transactions with or for the Funds, and may receive compensation for such services. The Funds may also make brokerage and other payments to Entities in connection with the Funds’ portfolio investment transactions. BlackRock or one or more Affiliates or Entities may engage in proprietary trading and advise accounts and funds that have investment objectives similar to those of the Funds and/or that engage in and compete for transactions in the same types of securities, currencies and other instruments as the Funds. This may include transactions in securities issued by other open-end and closed-end investment companies (which may include investment companies that are affiliated with the Funds and BlackRock, to the extent permitted under the Investment Company Act). The trading activities of BlackRock and these Affiliates or Entities are carried out without reference to positions held directly or indirectly by the Funds and may result in BlackRock or an Affiliate or an Entity having positions in certain securities that are senior or junior to, or have interests different from or adverse to, the securities that are owned by the Funds.

Neither BlackRock nor any Affiliate is under any obligation to share any investment opportunity, idea or strategy with the Funds. As a result, an Affiliate may compete with the Funds for appropriate investment opportunities. The results of the Funds’ investment activities, therefore, may differ from those of an Affiliate and of other accounts managed by an Affiliate, and it is possible that the Funds could sustain losses during periods in which one or more Affiliates and other accounts achieve profits on their trading for proprietary or other accounts. The opposite result is also possible.

In addition, the Funds may, from time to time, enter into transactions in which BlackRock or an Affiliate or an Entity or their directors, officers or employees or other clients have an adverse interest. Furthermore, transactions undertaken by clients advised or managed by BlackRock, its Affiliates or Entities may adversely impact the Funds. Transactions by one or more clients or BlackRock, its Affiliates or Entities or their directors, officers or employees, may have the effect of diluting or otherwise disadvantaging the values, prices or investment strategies of the Funds. The Funds’ activities may be limited because of regulatory restrictions applicable to BlackRock, one or more Affiliates or Entities and/or their internal policies designed to comply with such restrictions.

Under a securities lending program approved by the Board, the Corporation, on behalf of the Funds, has retained BlackRock Investment Management, LLC (“BIM”), an Affiliate of BlackRock, to serve as the securities lending agent for the Funds to the extent that the Funds participate in the securities lending program. For these services, the securities lending agent will receive a fee from the Funds, including a fee based on the returns earned on the Fund’s investment of the cash received as collateral for the loaned securities. In addition, one or more Affiliates or Entities may be among the entities to which the Funds may lend their portfolio securities under the securities lending program.

The activities of BlackRock, its Affiliates and Entities and their respective directors, officers or employees, may give rise to other conflicts of interest that could disadvantage the Funds and their shareholders. BlackRock has adopted policies and procedures designed to address these potential conflicts of interest. See the SAI for further information.

Valuation of Fund Investments

When you buy shares, you pay the net asset value, plus any applicable sales charge. This is the offering price. Shares are also redeemed at their net asset value, minus any applicable deferred sales charge or redemption fee. Each Fund calculates the net asset value of each class of its shares each day the NYSE is open, generally as of the close of regular trading hours on the NYSE, based on prices at the time of closing. The NYSE generally closes at 4:00 p.m. (Eastern time). The net asset value used in determining your share price is the next one calculated after your purchase or redemption order is received.

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Generally, Institutional Shares will have the highest net asset value because that class has the lowest expenses. Investor A Shares will have a higher net asset value than Investor C Shares. Also, dividends paid on Investor A and Institutional Shares will generally be higher than dividends paid on Investor C Shares because Investor A and Institutional Shares have lower expenses.

Equity securities and other instruments for which market quotations are readily available are valued at market value, which is generally determined using the last reported closing price or, if a reported closing price is not available, the last traded price on the exchange or market on which the security or instrument is primarily traded at the time of valuation. Each Fund values fixed-income portfolio securities and non-exchange traded derivatives using last available bid prices or current market quotations provided by dealers or prices (including evaluated prices) supplied by the Fund’s approved independent third-party pricing services, each in accordance with valuation procedures approved by the Board. Pricing services may use matrix pricing or valuation models that utilize certain inputs and assumptions to derive values. Pricing services generally value fixed-income securities assuming orderly transactions of institutional round lot size, but a Fund may hold or transact in such securities in smaller, odd lot sizes. Odd lots may trade at lower prices than institutional round lots. Short-term debt securities with remaining maturities of 60 days or less may be valued on the basis of amortized cost.

Foreign currency exchange rates are generally determined as of the close of business on the NYSE. Foreign securities owned by a Fund may trade on weekends or other days when the Fund does not price its shares. As a result, a Fund’s net asset value may change on days when you will not be able to purchase or redeem the Fund’s shares.

Generally, trading in foreign securities, U.S. Government securities, money market instruments and certain fixed-income securities is substantially completed each day at various times prior to the close of business on the NYSE. The values of such securities used in computing the net asset value of a Fund’s shares are determined as of such times.

When market quotations are not readily available or are not believed by BlackRock to be reliable, a Fund’s investments are valued at fair value. Fair value determinations are made by BlackRock in accordance with procedures approved by the Board. BlackRock may conclude that a market quotation is not readily available or is unreliable if a security or other asset or liability does not have a price source due to its lack of liquidity, if BlackRock believes a market quotation from a broker-dealer or other source is unreliable, where the security or other asset or other liability is thinly traded (e.g., municipal securities, certain small cap and emerging growth companies, and certain non-U.S. securities) or where there is a significant event subsequent to the most recent market quotation. For this purpose, a “significant event” is deemed to occur if BlackRock determines, in its business judgment prior to or at the time of pricing a Fund’s assets or liabilities, that it is likely that the event will cause a material change to the last closing market price of one or more assets or liabilities held by the Fund. For instance, significant events may occur between the foreign market close and the close of business on the NYSE that may not be reflected in the computation of a Fund’s net assets. If such event occurs, those instruments may be fair valued. Similarly, foreign securities whose values are affected by volatility that occurs in U.S. markets on a trading day after the close of foreign securities markets may be fair valued.

For certain foreign securities, a third-party vendor supplies evaluated, systematic fair value pricing based upon the movement of a proprietary multi-factor model after the relevant foreign markets have closed. This systematic fair value pricing methodology is designed to correlate the prices of foreign securities following the close of the local markets to the price that might have prevailed as of a Fund’s pricing time.

Fair value represents a good faith approximation of the value of a security. The fair value of one or more securities may not, in retrospect, be the price at which those assets could have been sold during the period in which the particular fair values were used in determining a Fund’s net asset value.

The Funds may accept orders from certain authorized Financial Intermediaries or their designees. The Funds will be deemed to receive an order when accepted by the Financial Intermediary or designee, and the order will receive the net asset value next computed by the Fund after such acceptance. If the payment for a purchase order is not made by a designated later time, the order will be canceled and the Financial Intermediary could be held liable for any losses.

Dividends, Distributions and Taxes

BUYING A DIVIDEND

Unless your investment is in a tax-deferred account, you may want to avoid buying shares shortly before the Fund pays a dividend, although the impact on you will be significantly less than if you were invested in a fund paying fully taxable dividends. The reason? If you buy shares when a Fund has declared but not yet distributed ordinary income or capital gains, you will pay the full price for the shares and then receive a portion of the price back in the form of a taxable dividend. Before investing you may want to consult your tax adviser.

Each Fund will distribute net investment income, if any, monthly and net realized capital gain, if any, at least annually. Each Fund may also pay a special distribution at the end of the calendar year to comply with federal tax requirements. Dividends may be reinvested automatically in shares of the Fund at net asset value without a sales charge or may be taken in cash. If you would like to receive dividends in cash, contact your Financial Intermediary or the Fund. Although this cannot be predicted with any certainty, the Funds anticipate that a significant amount of their dividends, if any, will consist of capital gains. Capital gains may be taxable to you at different rates depending on how long the Fund held the assets sold.

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Each Fund intends to make income distributions, most of which will be excludable from gross income for federal income tax purposes. Some distributions may be taxable.

The Fund will purchase a municipal security only if it is accompanied by an opinion of counsel to the issuer, which is delivered on the date of issuance of the security, that the interest paid on such security is excludable from gross income for Federal income tax purposes. For purposes of each Fund’s investment strategies, municipal securities and municipal bonds do not include certain tax credit bonds or tax subsidy bonds issued by municipalities and/or states, the interest of which are generally taxable for Federal income tax purposes. Holders of tax credit bonds may be entitled to be allocated income tax credits of certain amounts. To the extent that the dividends distributed by a Fund are derived from bond interest income that is excludable from gross income for Federal income tax purposes, they are exempt from Federal income tax.

There is a possibility that events occurring after the date of issuance of a security, or after a Fund’s acquisition of a security, may result in a determination that the interest on that security is, in fact, includable in gross income for Federal income tax purposes retroactively to its date of issue. Such a determination may cause a portion of prior distributions received by shareholders to be taxable to those shareholders in the year of receipt.

Distributions derived from taxable interest income or capital gains on portfolio securities or derivative instruments, if any, will be subject to Federal income taxes. If you redeem or exchange Fund shares, you generally will be treated as having sold your shares and any gain on the transaction may be subject to tax. Certain investors may be subject to a Federal alternative minimum tax on dividends attributable to a Fund’s investments in private activity bonds.

Generally, within 60 days after the end of the calendar year, the Fund or your Financial Intermediary will tell you the amount of exempt-interest dividends, taxable dividends and capital gain dividends you received that year. Capital gain dividends are taxable as long term capital gains to you, regardless of how long you have held your shares in the Fund. The tax treatment of dividends from a Fund is the same whether you choose to receive them in cash or to have them reinvested in shares of the Fund.

You will pay tax on dividends from the Fund whether you receive them in cash or additional shares. If you redeem Fund shares or exchange them for shares of another fund, you generally will be treated as having sold your shares and any gain on the transaction may be subject to tax. Fund distributions derived from qualified dividend income, which consists of dividends received from U.S. corporations and qualifying foreign corporations, and from long-term capital gains are eligible for taxation at a maximum rate of 15% or 20% for individuals, depending on whether their income exceeds certain threshold amounts, which are adjusted annually for inflation.

A 3.8% Medicare tax is imposed on the net investment income (which includes, but is not limited to, interest, dividends and net gain from investments) of U.S. individuals with income exceeding $200,000, or $250,000 if married filing jointly, and of trusts and estates.

Your dividends and redemption proceeds will be subject to backup withholding tax if you have not provided a taxpayer identification number or social security number or the number you have provided is incorrect.

If you are neither a tax resident nor a citizen of the United States or if you are a foreign entity (other than a pass-through entity to the extent owned by U.S. persons), the Fund’s ordinary income dividends will generally be subject to a 30% U.S. withholding tax, unless a lower treaty rate applies. However, certain distributions reported by the Fund as capital gain dividends, interest-related dividends or short-term capital gain dividends and paid to a foreign shareholder may be eligible for an exemption from U.S. withholding tax.

Separately, a 30% withholding tax is currently imposed on U.S.-source dividends, interest and other income items paid to (i) certain foreign financial institutions and investment funds, and (ii) certain other foreign entities. To avoid withholding, foreign financial institutions and investment funds will generally either need to (a) collect and report to the IRS detailed information identifying their U.S. accounts and U.S. account holders, comply with due diligence procedures for identifying U.S. accounts and withhold tax on certain payments made to noncomplying foreign entities and account holders or (b) if an intergovernmental agreement is entered into and implementing legislation is adopted, comply with the agreement and legislation. Other foreign entities will generally either need to provide detailed information identifying each substantial U.S. owner or certify there are no such owners.

This section summarizes some of the consequences under current federal tax law of an investment in a Fund. It is not a substitute for individualized tax advice. Consult your tax adviser about the potential tax consequences of an investment in a Fund under all applicable tax laws.

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Financial Highlights

The Financial Highlights table is intended to help you understand each Fund’s financial performance for the periods shown. Certain information reflects the financial results for a single Fund share. The total returns in the tables represent the rate that an investor would have earned or lost on an investment in the indicated Fund (assuming reinvestment of all dividends and/or distributions). The information has been audited by Deloitte & Touche LLP, whose report, along with each Fund’s financial statements, is included in the indicated Fund’s Annual Report, which is available upon request.

Financial Highlights of BlackRock High Yield Municipal Fund

	Institutional
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 9.59	$ 9.54	$ 9.99	$ 9.28	$ 9.12
Net investment income^(a)	0.39	0.40	0.41	0.40	0.41
Net realized and unrealized gain (loss)	0.30	0.05	(0.46)	0.72	0.16
Net increase (decrease) from investment operations	0.69	0.45	(0.05)	1.12	0.57
Distributions from net investment income^(b)	(0.39)	(0.40)	(0.40)	(0.41)	(0.41)
Net asset value, end of year	$ 9.89	$ 9.59	$ 9.54	$ 9.99	$ 9.28
Total Return^(c)
Based on net asset value	7.36%	4.78%	(0.38)%	12.32%	6.27%
Ratios to Average Net Assets^(d)
Total expenses	0.71%	0.70%	0.71%	0.71%	0.70%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.68%	0.68%	0.66%	0.71%	0.70%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense, fees and amortization of offering costs^(e)	0.52%	0.54%	0.57%	0.65%	0.66%
Net investment income	4.03%	4.14%	4.24%	4.23%	4.37%
Supplemental Data
Net assets, end of year (000)	$780,811	$549,217	$516,247	$554,336	$327,422
Borrowings outstanding, end of year (000)	$ 75,301	$ 61,022	$ 60,043	$ 46,657	$ 26,216
Portfolio turnover rate	14%	25%	36%	19%	41%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	0.01%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock High Yield Municipal Fund (continued)

	Investor A
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 9.56	$ 9.52	$ 9.97	$ 9.26	$ 9.10
Net investment income^(a)	0.36	0.37	0.38	0.38	0.38
Net realized and unrealized gain (loss)	0.31	0.04	(0.45)	0.71	0.16
Net increase (decrease) from investment operations	0.67	0.41	(0.07)	1.09	0.54
Distributions from net investment income^(b)	(0.36)	(0.37)	(0.38)	(0.38)	(0.38)
Net asset value, end of year	$ 9.87	$ 9.56	$ 9.52	$ 9.97	$ 9.26
Total Return^(c)
Based on net asset value	7.21%	4.40%	(0.63)%	12.05%	6.00%
Ratios to Average Net Assets^(d)
Total expenses	0.98%	0.96%	0.94%	0.96%	0.97%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.95%	0.94%	0.91%	0.96%	0.97%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense, fees and amortization of offering costs^(e)	0.79%	0.80%	0.82%	0.90%	0.93%
Net investment income	3.76%	3.88%	4.00%	3.99%	4.11%
Supplemental Data
Net assets, end of year (000)	$345,255	$220,992	$201,212	$228,140	$156,348
Borrowings outstanding, end of year (000)	$ 75,301	$ 61,022	$ 60,043	$ 46,657	$ 26,216
Portfolio turnover rate	14%	25%	36%	19%	41%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	0.01%	—%

^(e)	Intere Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock High Yield Municipal Fund (concluded)

	Investor C
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 9.59	$ 9.55	$ 9.99	$ 9.28	$ 9.12
Net investment income^(a)	0.29	0.30	0.31	0.31	0.31
Net realized and unrealized gain (loss)	0.30	0.04	(0.44)	0.71	0.16
Net increase (decrease) from investment operations	0.59	0.34	(0.13)	1.02	0.47
Distributions from net investment income^(b)	(0.29)	(0.30)	(0.31)	(0.31)	(0.31)
Net asset value, end of year	$ 9.89	$ 9.59	$ 9.55	$ 9.99	$ 9.28
Total Return^(c)
Based on net asset value	6.28%	3.62%	(1.26)%	11.20%	5.20%
Ratios to Average Net Assets^(d)
Total expenses	1.74%	1.73%	1.70%	1.72%	1.72%
Total expenses after fees waived and/or reimbursed and paid indirectly	1.70%	1.69%	1.66%	1.72%	1.72%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense, fees and amortization of offering costs^(e)	1.54%	1.56%	1.57%	1.66%	1.68%
Net investment income	3.02%	3.13%	3.25%	3.23%	3.36%
Supplemental Data
Net assets, end of year (000)	$64,484	$60,065	$63,314	$71,527	$54,239
Borrowings outstanding, end of year (000)	$75,301	$61,022	$60,043	$46,657	$26,216
Portfolio turnover rate	14%	25%	36%	19%	41%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	0.01%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock National Municipal Fund

	Institutional
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.79	$ 10.88	$ 11.22	$ 10.86	$ 10.88
Net investment income^(a)	0.33	0.33	0.34	0.34	0.38
Net realized and unrealized gain (loss)	0.27	(0.09)	(0.34)	0.36	(0.02)
Net increase from investment operations	0.60	0.24	0.00	0.70	0.36
Distributions from net investment income^(b)	(0.33)	(0.33)	(0.34)	(0.34)	(0.38)
Net asset value, end of year	$ 11.06	$ 10.79	$ 10.88	$ 11.22	$ 10.86
Total Return^(c)
Based on net asset value	5.68%	2.23%	0.09%	6.68%	3.33%
Ratios to Average Net Assets^(d)
Total expenses	0.53%	0.52%	0.57%	0.60%	0.64%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.48%	0.44%	0.49%	0.58%	0.59%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense and fees	0.43% ^(e)	0.44%	0.48% ^(e)	0.57% ^(e)	0.55% ^(e)
Net investment income	3.04%	3.04%	3.15%	3.10%	3.47%
Supplemental Data
Net assets, end of year (000)	$4,063,258	$3,028,849	$3,225,595	$3,326,972	$2,088,580
Borrowings outstanding, end of year (000)	$ 324,360	$ —	$ —	$ —	$ 275,550
Portfolio turnover rate	77%	51%	83%	83%	28%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	—%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock National Municipal Fund (continued)

	Investor A
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.80	$ 10.88	$ 11.23	$ 10.87	$ 10.88
Net investment income^(a)	0.30	0.30	0.32	0.33	0.36
Net realized and unrealized gain (loss)	0.27	(0.08)	(0.35)	0.36	(0.01)
Net increase (decrease) from investment operations	0.57	0.22	(0.03)	0.69	0.35
Distributions from net investment income^(b)	(0.30)	(0.30)	(0.32)	(0.33)	(0.36)
Net asset value, end of year	$ 11.07	$ 10.80	$ 10.88	$ 11.23	$ 10.87
Total Return^(c)
Based on net asset value	5.41%	2.07%	(0.22)%	6.42%	3.26%
Ratios to Average Net Assets^(d)
Total expenses	0.82%	0.77%	0.81%	0.85%	0.90%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.73%	0.69%	0.70%	0.74%	0.75%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense and fees	0.68% ^(e)	0.69%	0.70% ^(e)	0.72% ^(e)	0.72% ^(e)
Net investment income	2.79%	2.79%	2.93%	2.97%	3.30%
Supplemental Data
Net assets, end of year (000)	$3,227,894	$2,730,622	$2,342,752	$2,669,101	$2,388,743
Borrowings outstanding, end of year (000)	$ 324,360	$ —	$ —	$ —	$ 275,550
Portfolio turnover rate	77%	51%	83%	83%	28%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	—%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock National Municipal Fund (concluded)

	Investor C
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.80	$ 10.88	$ 11.23	$ 10.87	$ 10.88
Net investment income^(a)	0.22	0.22	0.24	0.24	0.28
Net realized and unrealized gain (loss)	0.27	(0.08)	(0.35)	0.36	(0.01)
Net increase (decrease) from investment operations	0.49	0.14	(0.11)	0.60	0.27
Distributions from net investment income^(b)	(0.22)	(0.22)	(0.24)	(0.24)	(0.28)
Net asset value, end of year	$ 11.07	$ 10.80	$ 10.88	$ 11.23	$ 10.87
Total Return^(c)
Based on net asset value	4.63%	1.31%	(0.96)%	5.63%	2.49%
Ratios to Average Net Assets^(d)
Total expenses	1.51%	1.47%	1.51%	1.54%	1.59%
Total expenses after fees waived and/or reimbursed and paid indirectly	1.48%	1.43%	1.45%	1.49%	1.50%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense and fees	1.43% ^(e)	1.43%	1.44% ^(e)	1.47% ^(e)	1.47% ^(e)
Net investment income	2.06%	2.04%	2.19%	2.22%	2.55%
Supplemental Data
Net assets, end of year (000)	$270,445	$327,384	$382,703	$467,928	$397,945
Borrowings outstanding, end of year (000)	$324,360	$ —	$ —	$ —	$275,550
Portfolio turnover rate	77%	51%	83%	83%	28%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	—%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock Short-Term Municipal Fund

	Institutional
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.08	$ 10.12	$ 10.18	$ 10.11	$ 10.16
Net investment income^(a)	0.16	0.11	0.07	0.05	0.04
Net realized and unrealized gain (loss)	0.07	(0.04)	(0.06)	0.07	(0.05)
Net increase (decrease) from investment operations	0.23	0.07	0.01	0.12	(0.01)
Distributions ^(b)
From net investment income	(0.16)	(0.11)	(0.07)	(0.05)	(0.04)
From net realized gain	—	—	(0.00) ^(c)	(0.00) ^(c)	—
Total distributions	(0.16)	(0.11)	(0.07)	(0.05)	(0.04)
Net asset value, end of year	$ 10.15	$ 10.08	$ 10.12	$ 10.18	$ 10.11
Total Return^(d)
Based on net asset value	2.32%	0.71%	0.10%	1.15%	(0.11)%
Ratios to Average Net Assets
Total expenses	0.46%	0.49%	0.52%	0.52%	0.51%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.36%	0.36%	0.37%	0.40%	0.40%
Net investment income	1.61%	1.12%	0.66%	0.48%	0.42%
Supplemental Data
Net assets, end of year (000)	$350,720	$360,543	$357,427	$454,165	$492,702
Portfolio turnover rate	129%	153%	88%	67%	72%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Amount is greater than $(0.005) per share.
^(d)	Where applicable, assumes the reinvestment of distributions.

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Financial Highlights (continued)

Financial Highlights of BlackRock Short-Term Municipal Fund (continued)

	Investor A
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.08	$ 10.13	$ 10.18	$ 10.12	$ 10.16
Net investment income^(a)	0.14	0.09	0.04	0.02	0.01
Net realized and unrealized gain (loss)	0.07	(0.05)	(0.05)	0.06	(0.04)
Net increase (decrease) from investment operations	0.21	0.04	(0.01)	0.08	(0.03)
Distributions ^(b)
From net investment income	(0.14)	(0.09)	(0.04)	(0.02)	(0.01)
From net realized gain	—	—	(0.00) ^(c)	(0.00) ^(c)	—
Total distributions	(0.14)	(0.09)	(0.04)	(0.02)	(0.01)
Net asset value, end of year	$ 10.15	$ 10.08	$ 10.13	$ 10.18	$ 10.12
Total Return^(d)
Based on net asset value	2.08%	0.37%	(0.06)%	0.76%	(0.29)%
Ratios to Average Net Assets
Total expenses	0.67%	0.68%	0.72%	0.71%	0.70%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.60%	0.60%	0.63%	0.69%	0.69%
Net investment income	1.39%	0.85%	0.40%	0.19%	0.13%
Supplemental Data
Net assets, end of year (000)	$109,462	$61,444	$67,193	$78,879	$100,980
Portfolio turnover rate	129%	153%	88%	67%	72%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Amount is greater than $(0.005) per share.
^(d)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

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Financial Highlights (concluded)

Financial Highlights of BlackRock Short-Term Municipal Fund (concluded)

	Investor C
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 9.82	$ 9.86	$ 9.96	$ 9.95	$ 10.07
Net investment income (loss)^(a)	0.05	—	(0.04)	(0.06)	(0.07)
Net realized and unrealized gain (loss)	0.08	(0.03)	(0.06)	0.07	(0.05)
Net increase (decrease) from investment operations	0.13	(0.03)	(0.10)	0.01	(0.12)
Distributions ^(b)
From net investment income	(0.06)	(0.01)	—	—	—
From net realized gain	—	—	(0.00) ^(c)	(0.00) ^(c)	—
Total distributions	(0.06)	(0.01)	—	—	—
Net asset value, end of year	$ 9.89	$ 9.82	$ 9.86	$ 9.96	$ 9.95
Total Return^(d)
Based on net asset value	1.33%	(0.26)%	(0.96)%	0.11%	(1.19)%
Ratios to Average Net Assets
Total expenses	1.45%	1.46%	1.48%	1.48%	1.47%
Total expenses after fees waived and/or reimbursed and paid indirectly	1.36%	1.36%	1.39%	1.48%	1.47%
Net investment income (loss)	0.52%	0.01%	(0.41)%	(0.60)%	(0.70)%
Supplemental Data
Net assets, end of year (000)	$15,434	$16,825	$22,859	$31,251	$31,121
Portfolio turnover rate	129%	153%	88%	67%	72%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Amount is greater than $(0.005) per share.
^(d)	Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

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General Information

Shareholder Documents

Electronic Access to Annual Reports, Semi-Annual Reports and Prospectuses

Electronic copies of most financial reports and prospectuses are available on BlackRock’s website. Shareholders can sign up for e-mail notifications of annual and semi-annual reports and prospectuses by enrolling in the Fund’s electronic delivery program. To enroll:

Shareholders Who Hold Accounts with Investment Advisers, Banks or Brokerages: Please contact your Financial Intermediary. Please note that not all investment advisers, banks or brokerages may offer this service.

Shareholders Who Hold Accounts Directly With BlackRock:

■	Access the BlackRock website at http://www.blackrock.com/edelivery; and
■	Log into your account.

Delivery of Shareholder Documents

Each Fund delivers only one copy of shareholder documents, including prospectuses, shareholder reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is known as “householding” and is intended to eliminate duplicate mailings and reduce expenses. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please contact your Fund at (800) 441-7762.

Certain Fund Policies

Anti-Money Laundering Requirements

Each Fund is subject to the USA PATRIOT Act (the “Patriot Act”). The Patriot Act is intended to prevent the use of the U.S. financial system in furtherance of money laundering, terrorism or other illicit activities. Pursuant to requirements under the Patriot Act, each Fund is required to obtain sufficient information from shareholders to enable it to form a reasonable belief that it knows the true identity of its shareholders. This information will be used to verify the identity of investors or, in some cases, the status of Financial Intermediaries. Such information may be verified using third-party sources. This information will be used only for compliance with the Patriot Act or other applicable laws, regulations and rules in connection with money laundering, terrorism or economic sanctions.

Each Fund reserves the right to reject purchase orders from persons who have not submitted information sufficient to allow the Fund to verify their identity. Each Fund also reserves the right to redeem any amounts in the Fund from persons whose identity it is unable to verify on a timely basis. It is each Fund’s policy to cooperate fully with appropriate regulators in any investigations conducted with respect to potential money laundering, terrorism or other illicit activities.

BlackRock Privacy Principles

BlackRock is committed to maintaining the privacy of its current and former fund investors and individual clients (collectively, “Clients”) and to safeguarding their non-public personal information. The following information is provided to help you understand what personal information BlackRock collects, how we protect that information and why in certain cases we share such information with select parties.

If you are located in a jurisdiction where specific laws, rules or regulations require BlackRock to provide you with additional or different privacy-related rights beyond what is set forth below, then BlackRock will comply with those specific laws, rules or regulations.

BlackRock obtains or verifies personal non-public information from and about you from different sources, including the following: (i) information we receive from you or, if applicable, your Financial Intermediary, on applications, forms or other documents; (ii) information about your transactions with us, our affiliates, or others; (iii) information we receive from a consumer reporting agency; and (iv) from visits to our website.

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BlackRock does not sell or disclose to non-affiliated third parties any non-public personal information about its Clients, except as permitted by law, or as is necessary to respond to regulatory requests or to service Client accounts. These non-affiliated third parties are required to protect the confidentiality and security of this information and to use it only for its intended purpose.

We may share information with our affiliates to service your account or to provide you with information about other BlackRock products or services that may be of interest to you. In addition, BlackRock restricts access to non-public personal information about its Clients to those BlackRock employees with a legitimate business need for the information. BlackRock maintains physical, electronic and procedural safeguards that are designed to protect the non-public personal information of its Clients, including procedures relating to the proper storage and disposal of such information.

Statement of Additional Information

If you would like further information about each Fund, including how it invests, please see the SAI.

For a discussion of each Fund’s policies and procedures regarding the selective disclosure of its portfolio holdings, please see the SAI. The Funds make their top ten holdings available on a monthly basis at www.blackrock.com generally within 5 business days after the end of the month to which the information applies.

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Glossary

This glossary contains an explanation of some of the common terms used in this prospectus. For additional information about the Fund, please see the SAI.

Acquired Fund Fees and Expenses — fees and expenses charged by other investment companies in which a Fund invests a portion of its assets.

Annual Fund Operating Expenses — expenses that cover the costs of operating a Fund.

Custom High Yield Index — a customized benchmark that reflects the returns of the S&P^® Customized High Yield Municipal Bond Index for periods prior to January 1, 2013, and the returns of only those bonds in the S&P^® Customized High Yield Municipal Bond Index that have maturities greater than five years for periods subsequent to January 1, 2013.

Custom National Index — a customized benchmark that reflects the returns of the S&P^® Municipal Bond Index for periods prior to January 1, 2013, and the returns of only those bonds in the S&P^® Municipal Bond Index that have maturities greater than five years for periods subsequent to January 1, 2013.

Distribution Fees — fees used to support a Fund’s marketing and distribution efforts, such as compensating Financial Intermediaries, advertising and promotion.

Management Fee — a fee paid to BlackRock for managing a Fund.

Other Expenses — include accounting, transfer agency, custody, professional fees and registration fees.

Service Fees — fees used to compensate Financial Intermediaries for certain shareholder servicing activities.

Shareholder Fees — fees paid directly by a shareholder, including sales charges that you may pay when you buy or sell shares of a Fund.

S&P^® Limited Maturity Municipal Bond Index — includes all bonds in the S&P^®Municipal Bond Index with a remaining maturity of less than four years.

S&P^® Municipal Bond Index — is composed of bonds held by managed municipal bond fund customers of Standard & Poor’s Securities Pricing, Inc. that are priced daily. Bonds in the S&P^® Municipal Bond Index must have an outstanding par value of at least $2 million and a remaining maturity of not less than one month.

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Intermediary-Defined Sales Charge Waiver Policies

Merrill Lynch:

Effective April 10, 2017, shareholders purchasing Fund shares through a Merrill Lynch platform or account (excluding shares purchased from or through the Fund, the Fund’s distributor or any non-Merrill Lynch platform or account, even if Merrill Lynch serves as broker-dealer of record for such shares) will be eligible only for the following sales charge waivers (front-end sales charge waivers and CDSC waivers) and reductions, which may differ from those disclosed elsewhere in the prospectus or SAI.

Front-End Sales Charge Waivers for Investor A Shares available at Merrill Lynch

■	Shares purchased by employer-sponsored retirement, deferred compensation and employee benefit plans (including health savings accounts) and trusts used to fund those plans, provided that the shares are not held in a commission-based brokerage account and shares are held for the benefit of the plan/plan participants
■	Shares purchased by or through a 529 Plan

■	Shares purchased through a Merrill Lynch affiliated investment advisory program, or effective February 1, 2019, exchanges of shares purchased through such a Merrill Lynch program due to the holdings moving from such program to a Merrill Lynch brokerage (non-advisory) account

■	Shares purchased by third party investment advisors on behalf of their advisory clients through Merrill Lynch’s platform
■	Shares of funds purchased through the Merrill Edge Self-Directed platform
■	Shares purchased through reinvestment of capital gains distributions and dividend reinvestment when purchasing shares of the same fund (but not any other BlackRock Fund)
■	Shares exchanged from Investor C (i.e. level-load) Shares of the same Fund in the month of or following the 10-year anniversary of the purchase date
■	Shares purchased by employees and registered representatives of Merrill Lynch or its affiliates and their family members
■	Shares purchased by directors of the Fund, and employees of BlackRock or any of its affiliates, as described in the prospectus
■	Shares purchased from the proceeds of redemptions from another BlackRock Fund, provided (1) the repurchase occurs within 90 days following the redemption, (2) the redemption and purchase occur in the same account, and (3) redeemed shares were subject to a front-end or deferred sales charge (known as Rights of Reinstatement)

CDSC Waivers on Investor A and C Shares available at Merrill Lynch

■	Shares sold due to death or disability of the shareholder
■	Shares sold as part of a systematic withdrawal plan as described in the prospectus
■	Shares bought due to return of excess contributions from an IRA Account
■	Shares sold as part of a required minimum distribution for IRA and retirement accounts due to the shareholder reaching age 70½
■	Shares sold to pay Merrill Lynch fees but only if the transaction is initiated by Merrill Lynch
■	Shares acquired through a Right of Reinstatement
■	Investor A and C Shares of the Fund held in the following IRA or other retirement brokerage accounts: Traditional IRAs, Roth IRAs, Rollover IRAs, Inherited IRAs, SEP IRAs, SIMPLE IRAs, BASIC Plans, Educational Savings Accounts and Medical Savings Accounts, that are exchanged for Institutional Shares of the Fund due to transfer to certain fee based accounts or platforms

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■	Effective February 1, 2019, Investor A Shares sold, where such Investor A Shares were received as a result of exchanges of shares purchased through a Merrill Lynch affiliated investment advisory program due to the holdings moving from the program to a Merrill Lynch brokerage (non-advisory) account

Front-End Sales Charge Discounts Available at Merrill Lynch: Breakpoints, Rights of Accumulation & Letters of Intent

■	Breakpoints as described in the prospectus
■	Rights of Accumulation (ROA) entitle shareholders to breakpoint discounts that will be automatically calculated based on the aggregated holding of BlackRock Fund assets held by accounts within the purchaser’s household at Merrill Lynch. Eligible BlackRock Fund assets not held at Merrill Lynch may be included in the ROA calculation only if the shareholder notifies his or her financial advisor about such assets
■	Letters of Intent (LOI) allow for breakpoint discounts based on anticipated purchases of BlackRock Funds, through Merrill Lynch, over a 13-month period of time

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Ameriprise Financial:

Investor A Shares Front-End Sales Charge Waivers Available at Ameriprise Financial

The following information applies to Investor A Shares purchases if you have an account with or otherwise purchase Fund shares through Ameriprise Financial.

Effective June 1, 2018, shareholders purchasing Investor A shares through an Ameriprise Financial platform or account will be eligible for the following front-end sales charge waivers and discounts, which may differ from those disclosed elsewhere in this Fund’s prospectus or SAI:

■	Employer-sponsored retirement plans (e.g., 401(k) plans, 457 plans, employer-sponsored 403(b) plans, profit sharing and money purchase pension plans and defined benefit plans). For purposes of this provision, employer-sponsored retirement plans do not include SEP IRAs, Simple IRAs or SAR-SEPs
■	Shares purchased through an Ameriprise Financial investment advisory program (if an advisory or similar share class for such investment advisory program is not available)
■	Shares purchased by third party investment advisors on behalf of their advisory clients through Ameriprise Financial’s platform (if an advisory or similar share class for such investment advisory program is not available)
■	Shares purchased through reinvestment of capital gains distributions and dividend reinvestment when purchasing shares of the same fund (but not any other fund within BlackRock Funds)
■	Shares exchanged from Investor C Shares of the same fund in the month of or following the 10-year anniversary of the purchase date. To the extent that this prospectus elsewhere provides for a waiver with respect to such shares following a shorter holding period, that waiver will apply to exchanges following such shorter period. To the extent that this prospectus elsewhere provides for a waiver with respect to exchanges of Investor C Shares for load waived shares, that waiver will also apply to such exchanges
■	Shares purchased by employees and registered representatives of Ameriprise Financial or its affiliates and their immediate family members
■	Shares purchased by or through qualified accounts (including IRAs, Coverdell Education Savings Accounts, 401(k)s, 403(b) TSCAs subject to ERISA and defined benefit plans) that are held by a covered family member, defined as an Ameriprise financial advisor (“FA”) and/or the FA’s spouse, FA’s lineal ascendant (mother, father, grandmother, grandfather, great grandmother, great grandfather), FA’s lineal descendant (son, step-son, daughter, step-daughter, grandson, granddaughter, great grandson, great granddaughter) or any spouse of a covered family member who is a lineal descendant
■	Shares purchased from the proceeds of redemptions within BlackRock Funds, provided (1) the repurchase occurs within 90 days following the redemption, (2) the redemption and purchase occur in the same account, and (3) redeemed shares were subject to a front-end or deferred sales charge (i.e. Rights of Reinstatement)

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Morgan Stanley Wealth Management:

Morgan Stanley Wealth Management Investor A Share Front-End Sales Charge Waiver

Effective July 1, 2018, Morgan Stanley Wealth Management clients purchasing Investor A Shares of the Fund through Morgan Stanley’s transactional brokerage accounts are entitled to a waiver of the front-end sales charge in the following circumstances:

■	Employer-sponsored retirement plans (e.g., 401(k) plans, 457 plans, employer-sponsored 403(b) plans, profit sharing and money purchase pension plans and defined benefit plans). For purposes of this provision, employer-sponsored retirement plans does not include SEP IRAs, Simple IRAs, SAR-SEPs or Keogh plans
■	Morgan Stanley employee and employee-related accounts according to Morgan Stanley’s account linking rules
■	Shares purchased through reinvestment of dividends and capital gains distributions when purchasing shares of the same fund
■	Shares purchased through a Morgan Stanley self-directed brokerage account
■	Investor C Shares that are no longer subject to a contingent deferred sales charge and are exchanged for Investor A Shares of the same fund pursuant to Morgan Stanley Wealth Management’s share class conversion program
■	Shares purchased from the proceeds of redemptions within BlackRock Funds under a Rights of Reinstatement provision, provided the repurchase occurs within 90 days following the redemption, the redemption and purchase occur in the same account, and redeemed shares were subject to a front-end or deferred sales charge

Unless specifically described above, no other front-end sales charge waivers are available to mutual fund purchases by Morgan Stanley Wealth Management clients through Morgan Stanley’s transactional brokerage accounts.

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Raymond James & Associates, Inc., Raymond James Financial Services, Inc. and Each Entity’s Affiliates (“Raymond James”):

Effective March 1, 2019, shareholders purchasing Fund shares through a Raymond James platform or account, or through an introducing broker-dealer or independent registered investment adviser for which Raymond James provides trade execution, clearance, and/or custody services, will be eligible only for the following sales charge waivers (front-end sales charge waivers and CDSC waivers) and discounts, which may differ from those disclosed elsewhere in this prospectus or the SAI.

Front-End Sales Charge Waivers on Investor A Shares Available at Raymond James

■	Shares purchased in a Raymond James investment advisory program.
■	Shares purchased of the same Fund or another BlackRock Fund through a systematic reinvestment of capital gains distributions and dividend distributions.
■	Shares purchased by employees and registered representatives of Raymond James or its affiliates and their family members as designated by Raymond James.
■	Shares purchased from the proceeds of redemptions from another BlackRock Fund, provided (1) the repurchase occurs within 90 days following the redemption, (2) the redemption and purchase occur in the same account, and (3) redeemed shares were subject to a front-end or deferred sales charge (known as Rights of Reinstatement).
■	A shareholder in the Fund’s Investor C shares will have their shares converted at net asset value to Investor A shares of the Fund if the shares are no longer subject to a CDSC and the conversion is in line with the policies and procedures of Raymond James.

CDSC Waivers on Investor A and C Shares Available at Raymond James

■	Shares sold due to death or disability of the shareholder.
■	Shares sold as part of a systematic withdrawal plan as described in the Fund’s prospectus.
■	Shares bought due to return of excess contributions from an IRA Account.
■	Shares sold as part of a required minimum distribution for IRA and retirement accounts due to the shareholder reaching age 70½ as described in the Fund’s prospectus.
■	Shares sold to pay Raymond James fees but only if the transaction is initiated by Raymond James.
■	Shares acquired through a Right of Reinstatement.

Front-End Sales Charge Discounts Available at Raymond James: Breakpoints, Rights of Accumulation and/or Letters of Intent

■	Breakpoints as described in this prospectus.
■	Rights of accumulation which entitle shareholders to breakpoint discounts will be automatically calculated based on the aggregated holding of BlackRock Fund assets held by accounts within the purchaser’s household at Raymond James. Eligible BlackRock Fund assets not held at Raymond James may be included in the calculation of rights of accumulation only if the shareholder notifies his or her financial advisor about such assets.
■	Letters of intent which allow for breakpoint discounts based on anticipated purchases of BlackRock Funds over a 13-month time period. Eligible BlackRock Fund assets not held at Raymond James may be included in the calculation of letters of intent only if the shareholder notifies his or her financial advisor about such assets.

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For More Information

Funds and Service Providers

FUNDS

BlackRock Municipal Bond Fund, Inc.
BlackRock High Yield Municipal Fund
BlackRock National Municipal Fund
BlackRock Short-Term Municipal Fund
100 Bellevue Parkway
Wilmington, Delaware 19809

Written Correspondence:
P.O. Box 9819
Providence, Rhode Island 02940-8019

Overnight Mail:
4400 Computer Drive
Westborough, Massachusetts 01581

(800) 441-7762

MANAGER

BlackRock Advisors, LLC
100 Bellevue Parkway
Wilmington, Delaware 19809

TRANSFER AGENT

BNY Mellon Investment Servicing (US) Inc.
301 Bellevue Parkway
Wilmington, Delaware 19809

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Deloitte & Touche LLP
200 Berkeley Street
Boston, Massachusetts 02116

ACCOUNTING SERVICES PROVIDER

State Street Bank and Trust Company
One Lincoln Street
Boston, Massachusetts 02111

DISTRIBUTOR

BlackRock Investments, LLC
40 East 52nd Street
New York, New York 10022

CUSTODIAN

State Street Bank and Trust Company
One Lincoln Street
Boston, Massachusetts 02111

COUNSEL

Willkie Farr & Gallagher LLP
787 Seventh Avenue
New York, New York 10019-6099

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Additional Information

For more information:
This prospectus contains important information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference. More information about the Funds is available at no charge upon request. This information includes:

Annual/Semi-Annual Reports
These reports contain additional information about each of the Fund’s investments. The annual report describes a Fund’s performance, lists portfolio holdings, and discusses recent market conditions, economic trends and Fund investment strategies that significantly affected the Fund’s performance for the last fiscal year.

Statement of Additional Information
A Statement of Additional Information (“SAI”) for each Fund, dated October 28, 2019, has been filed with the Securities and Exchange Commission (the “SEC”). The SAI, which includes additional information about each Fund, may be obtained free of charge, along with each Fund’s annual and semi-annual reports, by calling (800) 441-7762. The SAI, as amended and/or supplemented from time to time, is incorporated by reference into this prospectus.

BlackRock Investor Services
Representatives are available to discuss account balance information, mutual fund prospectuses, literature, programs and services available. Hours: 8:00 a.m. to 6:00 p.m. (Eastern time), on any business day. Call: (800) 441-7762.

Purchases and Redemptions
Call your Financial Intermediary or BlackRock Investor Services at (800) 441-7762.

World Wide Web
General Fund information and specific Fund performance, including the SAI and annual/semi-annual reports, can be accessed free of charge at www.blackrock.com/prospectus. Mutual fund prospectuses and literature can also be requested via this website.

Written Correspondence
BlackRock Municipal Bond Fund, Inc.
P.O. Box 9819
Providence, Rhode Island 02940-8019

Overnight Mail
BlackRock Municipal Bond Fund, Inc.
4400 Computer Drive
Westborough, Massachusetts 01581

Internal Wholesalers/Broker Dealer Support
Available on any business day to support investment professionals. Call: (800) 882-0052.

Portfolio Characteristics and Holdings
A description of a Fund’s policies and procedures related to disclosure of portfolio characteristics and holdings is available in the SAI.

For information about portfolio holdings and characteristics, BlackRock fund shareholders and prospective investors may call (800) 882-0052.

Securities and Exchange Commission
You may also view and copy public information about the Funds, including the SAI, by visiting the EDGAR database on the SEC’s website (http://www.sec.gov). Copies of this information can be obtained, for a duplicating fee, by electronic request at the following e-mail address: publicinfo@sec.gov.

You should rely only on the information contained in this prospectus. No one is authorized to provide you with information that is different from information contained in this prospectus.

The SEC has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

BLACKROCK MUNICIPAL BOND FUND, INC.
INVESTMENT COMPANY ACT FILE # 811-02688
© BlackRock Advisors, LLC

PRO-10051-1019

OCTOBER 28, 2019

Prospectus

BlackRock Municipal Bond Fund, Inc. | Class K Shares

•	BlackRock High Yield Municipal Fund
	Class K: MKYHX
•	BlackRock National Municipal Fund
	Class K: BNMLX
•	BlackRock Short-Term Municipal Fund
	Class K: MPLMX

You may elect to receive all future reports in paper free of charge. If you hold accounts directly with BlackRock, you can call (800) 537-4942 to inform BlackRock that you wish to continue receiving paper copies of your shareholder reports. If you hold accounts through a financial intermediary, you can follow the instructions included with this disclosure, if applicable, or contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. Please note that not all financial intermediaries may offer this service. Your election to receive reports in paper will apply to all funds advised by BlackRock Advisors, LLC, BlackRock Fund Advisors or their affiliates, or all funds held with your financial intermediary, as applicable.

This Prospectus contains information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference.

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Prospectus. Any representation to the contrary is a criminal offense.

Not FDIC Insured • May Lose Value • No Bank Guarantee

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Fund Overview	Key facts and details about the Funds listed in this prospectus, including investment objectives, principal investment strategies, principal risk factors, fee and expense information and historical performance information
	Key Facts About BlackRock High Yield Municipal Fund	3
	Key Facts About BlackRock National Municipal Fund	9
	Key Facts About BlackRock Short-Term Municipal Fund	16

Details About the Funds	How Each Fund Invests	22
	Investment Risks	26

Account Information	Information about account services, sales charges and waivers, shareholder transactions, and distributions and other payments
	Details About the Share Class	34
	How to Buy, Sell, Exchange and Transfer Shares	35
	Funds’ Rights	40
	Short-Term Trading Policy	40

Management of the Funds	Information about BlackRock and the Portfolio Managers
	BlackRock	42
	Portfolio Manager Information	44
	Conflicts of Interest	45
	Valuation of Fund Investments	46
	Dividends, Distributions and Taxes	47

Financial Highlights	Financial Performance of the Funds	49

General Information	Shareholder Documents	52
	Certain Fund Policies	52
	Statement of Additional Information	53

Glossary	Glossary of Investment Terms	54

For More Information	Funds and Service Providers	Inside Back Cover
	Additional Information	Back Cover

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Fund Overview

Key Facts About BlackRock High Yield Municipal Fund

Investment Objective

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)		Class K Shares
Management Fee¹		0.47%
Distribution and/or Service (12b-1) Fees		None
Other Expenses		0.22%
Interest Expense	0.16%
Miscellaneous Other Expenses	0.06%
Acquired Fund Fees and Expenses²		0.01%
Total Annual Fund Operating Expenses²		0.70%
Fee Waivers and/or Expense Reimbursements^1,3		(0.04)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^1,3		0.66%

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Municipal Bond Fund, Inc. (the “Corporation”) or by a vote of a majority of the outstanding voting securities of the Fund.

The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses.

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.49% of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

	1 Year	3 Years	5 Years	10 Years
Class K Shares	$67	$220	$386	$867

Portfolio Turnover:

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Principal Investment Strategies of the Fund

Principal Risks of Investing in the Fund

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy

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	redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
■	Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

■	Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.

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	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. Class K Shares do not have a full calendar year of operations as of the date of this prospectus. As a result, the chart and the table give you a picture of the long-term performance for Institutional Shares of the Fund, which are not offered in this prospectus. The performance of Class K Shares would be substantially similar to Institutional Shares because Class K Shares and Institutional Shares invest in the same portfolio of securities and performance would differ only to the extent that Institutional Shares and Class K Shares have different expenses. The actual returns of Class K Shares would have been higher than those of Institutional Shares because Class K Shares have lower expenses than Institutional Shares. The table compares the Fund’s performance to that of the S&P^® Municipal Bond Index and the Custom High Yield Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

Institutional Shares

ANNUAL TOTAL RETURNS

BlackRock High Yield Municipal Fund
As of 12/31

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As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock High Yield Municipal Fund — Institutional Shares
Return Before Taxes	2.15%	6.95%	9.35%
Return After Taxes on Distributions	2.15%	6.94%	9.34%
Return After Taxes on Distributions and Sale of Fund Shares	2.96%	6.46%	8.73%
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
Custom High Yield Index¹ (Reflects no deduction for fees, expenses or taxes)	4.64%	7.21%	9.65%

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Walter O’Connor, CFA	2006	Managing Director of BlackRock, Inc.
Theodore R. Jaeckel, CFA	2006	Managing Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

Class K Shares of the Fund are available only to (i) certain employee benefit plans, such as health savings accounts, and certain employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (collectively, “Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of the Fund through a Financial Intermediary (as defined below) that has entered into an agreement with the Fund’s distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, banks and bank trusts, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares, (iv) fee-based advisory platforms of a Financial Intermediary that (a) has specifically acknowledged in a written agreement with the Fund’s distributor and/or its affiliate(s) that the Financial Intermediary shall offer such shares to fee-based advisory clients through an omnibus account held at the Fund or (b) transacts in the Fund’s shares through another intermediary that has executed such an agreement and (v) any other investors who met the eligibility criteria for BlackRock Shares or Class K Shares prior to August 15, 2016 and have continually held Class K Shares of the Fund in the same account since August 15, 2016.

You may purchase or redeem shares of the Fund each day the New York Stock Exchange is open. Purchase orders may also be placed by calling (800) 537-4942, by mail (c/o BlackRock Funds, P.O. Box 9819, Providence, Rhode Island 02940-8019), or online at www.blackrock.com. Institutional Investors are subject to a $5 million minimum initial investment requirement. Other investors, including Employer-Sponsored Retirement Plans, have no minimum initial investment requirement. There is no minimum investment amount for additional purchases.

Tax Information

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from a redemption or exchange of Fund shares will generally not be subject to U.S. federal income taxes until you withdraw or receive distributions from the plan. If you are not invested through such a plan, then the Fund’s dividends and gain from a redemption or exchange may be subject to U.S. federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor. The Fund intends to make distributions most of which will be excludable from gross income for federal income tax purposes.

Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a financial professional or selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock and its affiliates) (each a “Financial Intermediary”), the Fund and BlackRock Investments, LLC, the Fund’s distributor, or its affiliates may pay the Financial Intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the Financial Intermediary and your individual financial professional to recommend the Fund over another investment.

Class K Shares are only available through a Financial Intermediary if the Financial Intermediary will not receive from Fund assets, or the Fund’s distributor’s or an affiliate’s resources, any commission payments, shareholder servicing fees (including sub-transfer agent and networking fees), or distribution fees (including Rule 12b-1 fees) with respect to assets invested in Class K Shares.

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Fund Overview

Key Facts About BlackRock National Municipal Fund

Investment Objective

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)		Class K Shares
Management Fee¹		0.39%
Distribution and/or Service 12b-1 Fees		None
Other Expenses		0.07%
Interest Expense	0.05%
Miscellaneous Other Expenses	0.02%
Acquired Fund Fees and Expenses²		0.01%
Total Annual Fund Operating Expenses²		0.47%
Fee Waivers and/or Expense Reimbursements^1,3		(0.03)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^1,3		0.44%

²	The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund’s most recent annual report, which do not include Acquired Fund Fees and Expenses.

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.38% of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

	1 Year	3 Years	5 Years	10 Years
Class K Shares	$45	$148	$260	$589

Portfolio Turnover:

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Principal Investment Strategies of the Fund

Principal Risks of Investing in the Fund

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.

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	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
■	Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
	Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
	Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.

	Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
	Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
	Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.

■	Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed

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	of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.
■	Tender Option Bonds and Related Securities Risk — The Fund’s participation in tender option bond transactions may reduce the Fund’s returns and/or increase volatility. Investments in tender option bond transactions expose the Fund to counterparty risk and leverage risk. An investment in a tender option bond transaction typically will involve greater risk than an investment in a municipal fixed rate security, including the risk of loss of principal. Distributions on TOB Residuals will bear an inverse relationship to short-term municipal security interest rates. Distributions on TOB Residuals paid to the Fund will be reduced or, in the extreme, eliminated as short-term municipal interest rates

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rise and will increase when short-term municipal interest rates fall. TOB Residuals generally will underperform the market for fixed rate municipal securities in a rising interest rate environment. The Fund may invest in TOB Trusts on either a non-recourse or recourse basis. If the Fund invests in a TOB Trust on a recourse basis, it could suffer losses in excess of the value of its TOB Residuals.

Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the S&P^® Municipal Bond Index and the Custom National Index. Effective August 15, 2016, the Board of Directors of the Corporation approved the reclassification of BlackRock Shares of the Fund as Class K Shares. The returns for Class K Shares prior to August 15, 2016 reflects the performance of the share class when it was classified as BlackRock Shares. The performance information for periods prior to July 18, 2011, the commencement of operations of Class K Shares (when classified as BlackRock Shares), shows the performance of the Fund’s Institutional Shares. The performance of Class K Shares would be substantially similar to Institutional Shares because Class K Shares and Institutional Shares invest in the same portfolio of securities and performance would differ only to the extent that Institutional Shares and Class K Shares have different expenses. The actual returns of Class K Shares would have been higher than those of Institutional Shares because Class K Shares have lower expenses than Institutional Shares. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

Class K Shares

ANNUAL TOTAL RETURNS

BlackRock National Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 7.60% (quarter ended September 30, 2009) and the lowest return for a quarter was -4.64% (quarter ended December 31, 2010). The year-to-date return as of September 30, 2019 was 6.66%.

As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock National Municipal Fund — Class K Shares
Return Before Taxes	0.66%	4.06%	5.85%
Return After Taxes on Distributions	0.66%	4.06%	5.84%
Return After Taxes on Distributions and Sale of Fund Shares	1.67%	3.94%	5.55%
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
Custom National Index¹ (Reflects no deduction for fees, expenses or taxes)	1.20%	4.83%	5.47%

¹	The Custom National Index reflects the returns of the S&P^® Municipal Bond Index for periods prior to January 1, 2013, and the returns of only those bonds in the S&P^® Municipal Bond Index that have maturities greater than 5 years for periods subsequent to January 1, 2013.

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Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Walter O’Connor, CFA	1996	Managing Director of BlackRock, Inc.
Michael Kalinoski, CFA	2016	Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

Tax Information

Different income tax rules apply depending on whether you are invested through a qualified tax-exempt plan described in section 401(a) of the Internal Revenue Code of 1986, as amended. If you are invested through such a plan (and Fund shares are not “debt-financed property” to the plan), then the dividends paid by the Fund and the gain realized from a redemption or exchange of Fund shares will generally not be subject to U.S. federal income taxes until you withdraw or receive distributions from the plan. If you are not invested through such a plan, then the Fund’s dividends and gain from a redemption or exchange may be subject to U.S. federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor. The Fund intends to make distributions most of which will be excludable from gross income for federal income tax purposes.

Payments to Broker/Dealers and Other Financial Intermediaries

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Intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the Financial Intermediary and your individual financial professional to recommend the Fund over another investment.

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Fund Overview

Key Facts About BlackRock Short-Term Municipal Fund

Investment Objective

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class K Shares
Management Fee¹	0.29%
Distribution and/or Service (12b-1) Fees	None
Other Expenses	0.09%
Total Annual Fund Operating Expenses	0.38%
Fee Waivers and/or Expense Reimbursements^1,2	(0.07)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^1,2	0.31%

As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.31% of average daily net assets through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

	1 Year	3 Years	5 Years	10 Years
Class K Shares	$32	$115	$206	$474

Portfolio Turnover:

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Principal Investment Strategies of the Fund

Principal Risks of Investing in the Fund

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
	The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
	To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
	These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
	A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy

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	redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

■	High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance.
■	Illiquid Investments Risk — The Fund may invest up to an aggregate amount of 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.

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	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
	Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

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Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the S&P^® Municipal Bond Index and the S&P^® Limited Maturity Municipal Bond Index, which are relevant to the Fund because they have characteristics similar to the Fund’s investment strategies. Effective September 1, 2015, the Board of Directors of the Corporation approved the reclassification of BlackRock Shares of the Fund as Class K Shares. The returns for Class K Shares prior to September 1, 2015 reflects the performance of the share class when it was classified as BlackRock Shares. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

Class K Shares

ANNUAL TOTAL RETURNS

BlackRock Short-Term Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 1.45% (quarter ended March 31, 2009) and the lowest return for a quarter was -0.60% (quarter ended December 31, 2016). The year-to-date return as of September 30, 2019 was 1.85%.

As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock Short-Term Municipal Fund — Class K Shares
Return Before Taxes	1.59%	0.62%	1.02%
Return After Taxes on Distributions	1.59%	0.61%	1.02%
Return After Taxes on Distributions and Sale of Fund Shares	1.51%	0.64%	1.01%

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As of 12/31/18 Average Annual Total Returns	1 Year	5 Years	10 Years
S&P ^® Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.36%	3.88%	5.11%
S&P ^® Limited Maturity Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)	1.76%	1.00%	1.59%

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Kevin A. Schiatta, CFA	2016	Director of BlackRock, Inc.
Kristi Manidis	2019	Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

Tax Information

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Payments to Broker/Dealers and Other Financial Intermediaries

Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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Details About the Funds

How Each Fund Invests

Investment Process

With respect to each Fund, BlackRock Advisors, LLC (“BlackRock”) considers a variety of factors when choosing investments, such as:

■	Credit Quality of Issuers — based on bond ratings and other factors, including economic and financial conditions.
■	Yield Analysis — takes into account factors such as the different yields available on different types of obligations and the shape of the yield curve (longer term obligations typically have higher yields).
■	Maturity Analysis — the weighted average maturity of the portfolio will be maintained within a desirable range as determined from time to time. Factors considered include portfolio activity, maturity of the supply of available bonds and the shape of the yield curve. Maturity of a debt security refers to the date upon which debt securities are due to be repaid, that is, the date when the issuer generally must pay back the face amount of the security.

The Funds intend to invest so that no more than 25% of a Fund’s assets are represented by the municipal securities of issuers located in the same state.

High Yield Fund

Investment Objective

The investment objective of the High Yield Fund is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Principal Investment Strategies

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municipal bonds rated BBB or Baa or lower if Fund management determines that there is an insufficient supply of such obligations available for investment.

ABOUT THE PORTFOLIO MANAGEMENT OF THE HIGH YIELD FUND

National Fund

Investment Objective

Principal Investment Strategies

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ABOUT THE PORTFOLIO MANAGEMENT OF THE NATIONAL FUND

Short-Term Fund

Investment Objective

Principal Investment Strategies

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ABOUT THE PORTFOLIO MANAGEMENT OF THE SHORT-TERM FUND

Other Strategies

In addition to the principal strategies discussed above, each Fund may also invest or engage in the following investments/strategies:

■

■	Indexed Securities — Each Fund may invest in securities the potential return of which is directly related to changes in an underlying index or interest rate, known as indexed securities. The return on indexed securities will rise when the underlying index rises and fall when the index falls.
■	Investment Companies — Each Fund has the ability to invest in other investment companies, such as exchange-traded funds, unit investment trusts, and open-end and closed-end funds. Each Fund may invest in affiliated investment companies, including affiliated money market funds and affiliated exchange-traded funds.

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■	Securities Lending — Each Fund may lend securities with a value up to 33¹⁄3% of its total assets to financial institutions that provide cash or securities issued or guaranteed by the U.S. Government as collateral.
■	Taxable Income — Investments in taxable money market securities as well as some of the derivatives discussed herein may cause a Fund to have taxable investment income. Each Fund may also realize capital gains on the sale of its municipal bonds (and other securities it holds). These capital gains will be taxable regardless of whether they are derived from a sale of municipal bonds.
■	Taxable Money Market Securities — Each Fund may invest up to 20% of its assets on a temporary basis in taxable money market securities that have a maturity of one year or less. Each Fund may make these investments for liquidity purposes or as a temporary investment pending an investment in municipal bonds.
■	Temporary Defensive Strategies — As a temporary measure for defensive purposes, a Fund may invest without limitation in taxable money market securities. These investments may prevent a Fund from meeting its investment objective.
■	When-Issued and Delayed Delivery Securities and Forward Commitments — The purchase or sale of securities on a when-issued basis, on a delayed delivery basis or through a forward commitment involves the purchase or sale of securities by a Fund at an established price with payment and delivery taking place in the future. Each Fund enters into these transactions to obtain what is considered an advantageous price to the Fund at the time of entering into the transaction.

High Yield Fund Other Strategies

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	Fund. The Fund may invest in TOB Residuals and may also invest in TOB Floaters. The Fund will look through to the underlying municipal bond held by a TOB Trust for purposes of the Fund’s 80% policy.
■	Variable Rate Demand Obligations — The High Yield Fund may invest in variable rate demand obligations, which are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution.

National Fund Other Strategies

■	Variable Rate Demand Obligations — The National Fund may invest in variable rate demand obligations, which are floating rate securities that combine an interest in a long term municipal bond with a right to demand payment before maturity from a bank or other financial institution.

Short-Term Fund Other Strategies

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Investment Risks

Principal Risks of Investing in a Fund:

■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.

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■	Derivatives Risk (National Fund Principal Risk; High Yield Fund and Short-Term Fund Other Risk) — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
	Volatility Risk — The Fund’s use of derivatives may reduce the Fund’s returns and/or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
	Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.

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Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

Risks Specific to Certain Derivatives Used by the Fund

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rates, currency exchange rates and other economic factors; and (e) the possibility that the counterparty will default in the performance of its obligations.

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■	Junk bonds may be issued by less creditworthy issuers. Issuers of junk bonds may have a larger amount of outstanding debt relative to their assets than issuers of investment grade bonds. In the event of an issuer’s bankruptcy, claims of other creditors may have priority over the claims of junk bond holders, leaving few or no assets available to repay junk bond holders.
■	Prices of junk bonds are subject to extreme price fluctuations. Adverse changes in an issuer’s industry and general economic conditions may have a greater impact on the prices of junk bonds than on other higher rated fixed-income securities.
■	Issuers of junk bonds may be unable to meet their interest or principal payment obligations because of an economic downturn, specific issuer developments, or the unavailability of additional financing.

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■	Junk bonds frequently have redemption features that permit an issuer to repurchase the security from the Fund before it matures. If the issuer redeems junk bonds, the Fund may have to invest the proceeds in bonds with lower yields and may lose income.

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■	The Fund may incur expenses to the extent necessary to seek recovery upon default or to negotiate new terms with a defaulting issuer.

■

■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:
	General Obligation Bonds Risks — The full faith, credit and taxing power of the municipality that issues a general obligation bond secures payment of interest and repayment of principal. Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
	Revenue Bonds Risks — Payments of interest and principal on revenue bonds are made only from the revenues generated by a particular facility, class of facilities or the proceeds of a special tax or other revenue source. These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
	Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its full faith, credit and taxing power for repayment. If the private enterprise defaults on its payments, the Fund may not receive any income or get its money back from the investment.
	Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.
	Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. They may provide interim financing in anticipation of, and are secured by, tax collection, bond sales or revenue receipts. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
	Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. The issuer will generally appropriate municipal funds for that purpose, but is not obligated to do so. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property. However, if the issuer does not fulfill its payment obligation it may be difficult to sell the property and the proceeds of a sale may not cover the Fund’s loss.
	Tax-Exempt Status Risk — In making investments, the Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal obligations and payments under tax-exempt derivative securities. Neither the Fund nor its

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	investment manager will independently review the bases for those tax opinions. If any of those tax opinions are ultimately determined to be incorrect or if events occur after the security is acquired that impact the security’s tax-exempt status, the Fund and its shareholders could be subject to substantial tax liabilities. The IRS has generally not ruled on the taxability of the securities. An assertion by the IRS that a portfolio security is not exempt from U.S. federal income tax (contrary to indications from the issuer) could affect the Fund’s and its shareholders’ income tax liability for the current or past years and could create liability for information reporting penalties. In addition, an IRS assertion of taxability may impair the liquidity and the fair market value of the securities.
■	Tender Option Bonds and Related Securities Risk (National Fund Principal Risk; High Yield Fund Other Risk) — The Fund’s participation in tender option bond transactions may reduce the Fund’s returns and/or increase volatility. Investments in tender option bond transactions expose the Fund to counterparty risk and leverage risk. An investment in a tender option bond transaction typically will involve greater risk than an investment in a municipal fixed rate security, including the risk of loss of principal. Distributions on TOB Residuals will bear an inverse relationship to short-term municipal security interest rates. Distributions on TOB Residuals paid to the Fund will be reduced or, in the extreme, eliminated as short-term municipal interest rates rise and will increase when short-term municipal interest rates fall. TOB Residuals generally will underperform the market for fixed rate municipal securities in a rising interest rate environment.
	The Fund may invest in TOB Trusts on either a non-recourse or recourse basis. TOB Trusts are typically supported by a liquidity facility provided by a third-party bank or other financial institution (the “Liquidity Provider”) that allows the holders of the TOB Floaters to tender their certificates in exchange for payment of par plus accrued interest on any business day, subject to the non-occurrence of tender option termination events. When the Fund invests in a TOB Trust on a non-recourse basis, and the Liquidity Provider is required to make a payment under the liquidity facility, the Liquidity Provider will typically liquidate all or a portion of the municipal securities held in the TOB Trust and then fund the balance, if any, of the amount owed under the liquidity facility over the liquidation proceeds (the “Liquidation Shortfall”).
	If a Fund invests in a TOB Trust on a recourse basis, the Fund will typically enter into a reimbursement agreement with the Liquidity Provider where the Fund is required to reimburse the Liquidity Provider the amount of any Liquidation Shortfall. As a result, if the Fund invests in a TOB Trust on a recourse basis, the Fund will bear the risk of loss with respect to any Liquidation Shortfall.
	To the extent that the Fund, rather than a third-party bank or financial institution, sponsors a TOB Trust, certain responsibilities that previously belonged to the sponsor bank will be performed by, or on behalf of, the Fund. The Fund’s additional duties and responsibilities under the new TOB Trust structure may give rise to certain additional risks including compliance, securities law and operational risks.

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A Fund may also be subject to certain other non-principal risks associated with its investments and investment strategies, including:

■

■	Indexed and Inverse Securities Risk — Indexed and inverse securities provide a potential return based on a particular index of value or interest rates. The Fund’s return on these securities will be subject to risk with respect

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not meet its obligation. If this occurs, the Fund may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.

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Account Information

Details About the Share Class

Each Fund currently offers multiple share classes (Class K Shares in this prospectus), each with its own sales charge and expense structure, allowing you to invest in the way that best suits your needs. Each share class represents an ownership interest in the same investment portfolio of a Fund. When you choose your class of shares, you should consider the size of your investment and how long you plan to hold your shares. Only certain investors are eligible to buy Class K Shares. Either your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock and its affiliates) (each a “Financial Intermediary”) can help you determine whether you are eligible to buy Class K Shares.

Each Fund’s shares are distributed by BlackRock Investments, LLC (the “Distributor”), an affiliate of BlackRock.

The table below summarizes key features of Class K Shares of the Funds.

Class K Shares at a Glance


Availability	Available only to (i) certain employee benefit plans, such as health savings accounts, and certain employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (collectively, “Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of a Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, banks and bank trusts, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of a Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares, (iv) fee-based advisory platforms of a Financial Intermediary that (a) has specifically acknowledged in a written agreement with the Fund’s distributor and/or its affiliate(s) that the Financial Intermediary shall offer such shares to fee-based advisory clients through an omnibus account held at the Fund or (b) transacts in the Fund’s shares through another intermediary that has executed such an agreement and (v) any other investors who met the eligibility criteria for BlackRock Shares or Class K Shares prior to August 15, 2016 and have continually held Class K Shares of a Fund in the same account since August 15, 2016.
Minimum Investment	$5 million minimum initial investment for Institutional Investors. There is no minimum initial investment requirement for any Employer-Sponsored Retirement Plans or any other eligible investors other than Institutional Investors. There is no minimum investment amount for additional purchases.
Initial Sales Charge?	No. Entire purchase price is invested in shares of a Fund.
Deferred Sales Charge?	No.
Distribution and Service (12b-1) Fees?	No.
Redemption Fees?	No.

Each Fund reserves the right to modify or waive the above-stated policies at any time.

When Class K Shares are purchased through a customer’s account in an Employer-Sponsored Retirement Plan through procedures established by the Employer-Sponsored Retirement Plan, confirmation of share purchases and redemptions will be sent to the Employer-Sponsored Retirement Plan. A customer’s ownership of shares will be recorded by the Employer-Sponsored Retirement Plan and reflected in the account statements provided by the Employer-Sponsored Retirement Plan to its participants.

If you purchased your shares through an Employer-Sponsored Retirement Plan and you transfer your investment from an Employer-Sponsored Retirement Plan to a type of account, such as an individual retirement account, that is not an eligible Class K Share investor in a Fund, you must liquidate your investment in Class K Shares of the Fund and

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purchase a share class of the Fund or another fund advised by BlackRock or its affiliates that is available for purchase by that type of account.

For investors not purchasing shares through an Employer-Sponsored Retirement Plan, please see below for information on how to buy, sell, exchange and transfer shares.

Right of Accumulation

i.	The current value of an investor’s existing Investor A and A1, Investor C, C1, C2 and C3, Investor P, Institutional, Class K and Premier Shares in most mutual funds sponsored and advised by BlackRock or its affiliates (“BlackRock Funds”),
ii.	The current value of an investor’s existing shares of certain unlisted closed-end management investment companies sponsored and advised by BlackRock or its affiliates and
iii.	The investment in the BlackRock CollegeAdvantage 529 Program by the investor or by or on behalf of the investor’s spouse and children.

Financial Intermediaries may value current holdings of their customers differently for purposes of determining whether an investor qualifies for a breakpoint and a reduced front-end sales charge, although customers of the same Financial Intermediary will be treated similarly. In order to use this right, the investor must alert BlackRock to the existence of any previously purchased shares.

How to Buy, Sell, Exchange and Transfer Shares

The chart on the following pages summarizes how to buy, sell, exchange and transfer shares through your Financial Intermediary. If you are not purchasing shares through an Employer-Sponsored Retirement Plan, you may also buy, sell, exchange and transfer shares through BlackRock, if your account is held directly with BlackRock. To learn more about buying, selling, exchanging or transferring shares through BlackRock, call (800) 537-4942. Because the selection of a mutual fund involves many considerations, your Financial Intermediary may help you with this decision.

With certain limited exceptions, the Funds are generally available only to investors residing in the United States and may not be distributed by a foreign Financial Intermediary. Under this policy, in order to accept new accounts or additional investments (including by way of exchange from another BlackRock Fund) into existing accounts, a Fund generally requires that (i) a shareholder that is a natural person be a U.S. citizen or resident alien, in each case residing within the United States or a U.S. territory (including APO/FPO/DPO addresses), and have a valid U.S. taxpayer identification number, and (ii) a Financial Intermediary or a shareholder that is an entity be domiciled in the United States and have a valid U.S. taxpayer identification number or be domiciled in a U.S. territory and have a valid U.S. taxpayer identification number or IRS Form W-8. Any existing account that is updated to reflect a non-U.S. address will also be restricted from making additional investments.

Each Fund may reject any purchase order, modify or waive the minimum initial or subsequent investment requirements for any shareholders and suspend and resume the sale of any share class of the Fund at any time for any reason. In addition, each Fund may waive certain requirements regarding the purchase, sale, exchange or transfer of shares described below.

Under certain circumstances, if no activity occurs in an account within a time period specified by state law, a shareholder’s shares in a Fund may be transferred to that state.

How to Buy Shares

	Your Choices	Important Information for You to Know
Initial Purchase	Determine the amount of your investment	There is no minimum initial investment for any Employer-Sponsored Retirement Plans or any other investors other than Institutional Investors. For Institutional Investors, there is a $5 million minimum initial investment for all accounts.

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	Your Choices	Important Information for You to Know
Initial Purchase (continued)	Have your Financial Intermediary submit your purchase order	The price of your shares is based on the next calculation of the Fund’s net asset value after your order is placed. Any purchase orders placed prior to the close of business on the New York Stock Exchange (the “NYSE”) (generally 4:00 p.m. Eastern time) will be priced at the net asset value determined that day. Certain Financial Intermediaries, however, may require submission of orders prior to that time. Purchase orders placed after that time will be priced at the net asset value determined on the next business day. A broker-dealer or financial institution maintaining the account in which you hold shares may charge a separate account, service or transaction fee on the purchase or sale of Fund shares that would be in addition to the fees and expenses shown in the Fund’s “Fees and Expenses” table. Each Fund may reject any order to buy shares and may suspend the sale of shares at any time. Certain Financial Intermediaries may charge a processing fee to confirm a purchase.
	Or contact BlackRock (for accounts held directly with BlackRock)	For investors not purchasing shares through an Employer-Sponsored Retirement Plan, to purchase shares directly from BlackRock, call (800) 537-4942 and request a new account application.
Add to Your Investment	Purchase additional shares	There is no minimum investment amount for additional purchases.
	Have your Financial Intermediary submit your purchase order for additional shares	To purchase additional shares, you may contact your Financial Intermediary or Employer-Sponsored Retirement Plan.
	Or contact BlackRock (for accounts held directly with BlackRock)	For investors not purchasing shares through an Employer-Sponsored Retirement Plan: Purchase by Telephone: Call the Fund at (800) 537-4942 and speak with one of our representatives. The Fund has the right to reject any telephone request for any reason. Purchase by Internet: You may purchase your shares, and view activity in your account, by logging onto the BlackRock website at www.blackrock.com. Purchases made on the Internet using the Automated Clearing House (“ACH”) will have a trade date that is the day after the purchase is made. Certain institutional clients’ purchase orders placed by wire prior to the close of business on the NYSE will be priced at the net asset value determined that day. Contact your Financial Intermediary or BlackRock for further information. Limits on amounts that may be purchased via Internet may vary. For additional information call BlackRock at (800) 537-4942. Please read the On-Line Services Disclosure Statement and User Agreement, the Terms and Conditions page and the Consent to Electronic Delivery Agreement (if you consent to electronic delivery), before attempting to transact online. Each Fund employs reasonable procedures to confirm that transactions entered over the Internet are genuine. By entering into the User Agreement with the Fund in order to open an account through the website, the shareholder waives any right to reclaim any losses from the Fund or any of its affiliates incurred through fraudulent activity.
	Acquire additional shares by reinvesting dividends and capital gains	All dividends and capital gains distributions are automatically reinvested without a sales charge. To make any changes to your dividend and/or capital gains distributions options, please call BlackRock at (800) 537-4942 (for investors who are not purchasing shares through an Employer-Sponsored Retirement Plan) or contact your Financial Intermediary.

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	Your Choices	Important Information for You to Know
How to Pay for Shares	Making payment for purchases	If you are purchasing shares through an Employer-Sponsored Retirement Plan, payment for an order must be made in Federal funds or other immediately available funds by the time specified by your Financial Intermediary, but in no event later than 4:00 p.m. (Eastern time) on the first business day following the receipt of the order. If payment is not received by this time, the order will be canceled and you and your Financial Intermediary will be responsible for any loss to the Fund. If you are not purchasing shares through an Employer-Sponsored Retirement Plan, payment for shares must normally be made in Federal funds or other immediately available funds by the time specified by your Financial Intermediary but in no event later than 4:00 p.m. (Eastern time) on the first business day following the receipt of the order. Payment may also, at the discretion of the Fund, be made in the form of securities that are permissible investments for the respective fund. If payment is not received by this time, the order will be canceled and you and your Financial Intermediary will be responsible for any loss to the Fund.

How to Sell Shares

	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares	Have your Financial Intermediary submit your sales order	If you purchased shares through an Employer-Sponsored Retirement Plan, you can make redemption requests through your Financial Intermediary in accordance with the procedures applicable to your accounts. These procedures may vary according to the type of account and the Financial Intermediary involved, and customers should consult their Financial Intermediary in this regard. Financial Intermediaries are responsible for transmitting redemption orders and crediting their customers’ accounts with redemption proceeds on a timely basis. Information relating to such redemption services and charges to process a redemption of shares, if any, should be obtained by customers from their Financial Intermediaries. If you did not purchase your shares through an Employer-Sponsored Retirement Plan, you can make redemption requests through your Financial Intermediary. The price of Class K Shares is based on the next calculation of the Fund’s net asset value after your order is placed. For your redemption request to be priced at the net asset value on the day of your request, you must submit your request to your Financial Intermediary prior to that day’s close of business on the NYSE (generally, 4:00 p.m. Eastern time). Certain Financial Intermediaries, however, may require submission of orders prior to that time. Any redemption request placed after that time will be priced at the net asset value at the close of business on the next business day. Regardless of the method the Fund uses to make payment of your redemption proceeds (check or wire), your redemption proceeds typically will be sent one to two business days after your request is submitted, but in any event, within seven days. Certain Financial Intermediaries may charge a fee to process a redemption of shares. The Fund may reject an order to sell shares under certain circumstances.
	Selling shares held directly with BlackRock	Methods of Redeeming if You Did Not Purchase Your Shares Through an Employer-Sponsored Retirement Plan Redeem by Telephone: You may sell shares held at BlackRock by telephone request. Call (800) 537-4942 for details. The Fund, its administrator and the Distributor will employ reasonable procedures to confirm that instructions communicated by telephone are genuine. The Fund and its service providers will not be liable for any loss, liability, cost or expense for acting upon telephone instructions

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Selling shares held directly with BlackRock (continued)	that are reasonably believed to be genuine in accordance with such procedures. The Fund may refuse a telephone redemption request if it believes it is advisable to do so. During periods of substantial economic or market change, telephone redemptions may be difficult to complete. Please find below alternative redemption methods. Redeem by Internet: You may redeem in your account, by logging onto the BlackRock website at www.blackrock.com. Proceeds from Internet redemptions will be sent via wire to the bank account of record. Redeem in Writing: Redemption requests may be sent in proper form to BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019 or for overnight delivery, 4400 Computer Drive, Westborough, Massachusetts 01581. Under certain circumstances, a medallion signature guarantee will be required. Payment of Redemption Proceeds Redemption proceeds may be paid by check or, if the Fund has verified banking information on file, by wire transfer. Payment by Check: BlackRock will normally mail redemption proceeds within three business days following receipt of a properly completed request, but in any event within seven days. Shares can be redeemed by telephone and the proceeds sent by check to the shareholder at the address on record. Shareholders will pay $15 for redemption proceeds sent by check via overnight mail. You are responsible for any additional charges imposed by your bank for this service. The Fund reserves the right to reinvest any dividend or distribution amounts (e.g., income dividends or capital gains) which you have elected to receive by check should your check be returned as undeliverable or remain uncashed for more than 6 months. No interest will accrue on amounts represented by uncashed checks. Your check will be reinvested in your account at the net asset value next calculated, on the day of the investment. When reinvested, those amounts are subject to the risk of loss like any fund investment. If you elect to receive distributions in cash and a check remains undeliverable or uncashed for more than 6 months, your cash election may also be changed automatically to reinvest and your future dividend and capital gains distributions will be reinvested in the Fund at the net asset value as of the date of payment of the distribution. Payment by Wire Transfer: Payment for redeemed shares for which a redemption order is received before 4:00 p.m. (Eastern time) on a business day is normally made in Federal funds wired to the redeeming shareholder on the next business day, provided that the Fund’s custodian is also open for business. Payment for redemption orders received after 4:00 p.m. (Eastern time) or on a day when the Fund’s custodian is closed is normally wired in Federal funds on the next business day following redemption on which the Fund’s custodian is open for business. The Fund reserves the right to wire redemption proceeds within seven days after receiving a redemption order if, in the judgment of the Fund, an earlier payment could adversely affect the Fund. Shares can be redeemed by Federal wire transfer to a single previously designated bank account. No charge for wiring redemption payments with respect to Class K Shares is imposed by the Fund. You are responsible for any additional charges imposed by your bank for wire transfers. The Fund is not responsible for the efficiency of the Federal wire system or the shareholder’s firm or bank. To change the name of the single, designated bank account to receive wire redemption proceeds, it is necessary to send a written request to the Fund at the address on the back cover of this prospectus. ***

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Selling shares held directly with BlackRock (continued)	If you make a redemption request before the Fund has collected payment for the purchase of shares, the Fund may delay mailing your proceeds. This delay will usually not exceed ten days.
Redemption Proceeds		Under normal circumstances, the Fund expects to meet redemption requests by using cash or cash equivalents in its portfolio or by selling portfolio assets to generate cash. During periods of stressed market conditions, when a significant portion of the Fund’s portfolio may be comprised of less-liquid investments, the Fund may be more likely to limit cash redemptions and may determine to pay redemption proceeds by (i) borrowing under a line of credit it has entered into with a group of lenders, (ii) borrowing from another BlackRock Fund pursuant to an interfund lending program, to the extent permitted by the Fund’s investment policies and restrictions as set forth in the SAI, and/or (iii) transferring portfolio securities in-kind to you. The SAI includes more information about the Fund’s line of credit and interfund lending program, to the extent applicable. If the Fund pays redemption proceeds by transferring portfolio securities in-kind to you, you may pay transaction costs to dispose of the securities, and you may receive less for them than the price at which they were valued for purposes of redemption.

How to Exchange Shares or Transfer Your Account

	Your Choices	Important Information for You to Know
Exchange Privilege	Selling shares of one BlackRock Fund to purchase shares of another BlackRock Fund (“exchanging”)	Class K Shares of the Fund are generally exchangeable for shares of the same class of another BlackRock Fund, to the extent such shares are offered by your Financial Intermediary. Investors who currently own Class K Shares of the Fund may make exchanges into Class K Shares of other BlackRock Funds except for investors holding shares through certain client accounts at Financial Intermediaries that are omnibus with the Fund and do not meet applicable minimums. There is no required minimum amount with respect to exchanges of Class K Shares. You may only exchange into Class K Shares of a BlackRock Fund that is open to new investors or in which you have a current account, if the BlackRock Fund is closed to new investors. To exercise the exchange privilege, you may contact your Financial Intermediary. Alternatively, if your account is held directly with BlackRock, you may: (i) call (800) 537-4942 and speak with one of our representatives, (ii) make the exchange via the Internet by accessing your account online at www.blackrock.com, or (iii) send a written request to the Fund at the address on the back cover of this prospectus. Please note, if you indicated on your new account application that you did not want the Telephone Exchange Privilege, you will not be able to place exchanges via the telephone until you update this option either in writing or by calling (800) 537-4942. The Fund has the right to reject any telephone request for any reason. Although there is currently no limit on the number of exchanges that you can make, the exchange privilege may be modified or terminated at any time in the future. The Fund may suspend or terminate your exchange privilege at any time for any reason, including if the Fund believes, in its sole discretion, that you are engaging in market timing activities. See “Short-Term Trading Policy” below. For U.S. federal income tax purposes a share exchange is a taxable event and a capital gain or loss may be realized. Please consult your tax adviser or other Financial Intermediary before making an exchange request.
Transfer Shares to Another Financial Intermediary	Transfer to a participating Financial Intermediary	You may transfer your Class K Shares of the Fund only to another Financial Intermediary that has entered into an agreement with the Distributor. Certain shareholder services may not be available for the transferred shares. All future trading of these assets must be coordinated by the receiving firm. Please contact your Financial Intermediary to accomplish the transfer of your Class K Shares.

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	Your Choices	Important Information for You to Know
	Transfer to a non-participating Financial Intermediary	You must either: • Transfer your Class K Shares to an account with the Fund; or • Sell your Class K Shares. Please contact your Financial Intermediary to accomplish the transfer of your Class K Shares.

Additional Purchase and Redemption Information Applicable to the Funds if You Are Not Purchasing Shares Through an Employer-Sponsored Retirement Plan

If you are not purchasing shares through an Employer-Sponsored Retirement Plan, a Fund may authorize one or more banks, savings and loan associations and other financial institutions (each a “Service Organization”) to accept purchase and redemption orders on its behalf. Such Service Organizations may be authorized to designate other intermediaries to accept purchase and redemption orders on the Fund’s behalf. If you purchase or redeem shares through a Service Organization or its designee, that entity may have its own deadlines for the receipt of the purchase or redemption order that may be earlier than those stated in the prospectus. The Fund will be deemed to have received a purchase or redemption order when a Service Organization or, if applicable, that Service Organization’s authorized designee, accepts the order. These orders will be priced at the Fund’s net asset value per share next calculated after they are so accepted.

Funds’ Rights

Each Fund may:

■	Suspend the right of redemption if trading is halted or restricted on the NYSE or under other emergency conditions described in the Investment Company Act;
■	Postpone the date of payment upon redemption if trading is halted or restricted on the NYSE or under other emergency conditions described in the Investment Company Act or if a redemption request is made before the Fund has collected payment for the purchase of shares;
■	Redeem shares for property other than cash as may be permitted under the Investment Company Act; and
■	Redeem shares involuntarily in certain cases, such as when the value of a shareholder account falls below a specified level.

Short-Term Trading Policy

The Board of Directors (the “Board”) has determined that the interests of long-term shareholders and each Fund’s ability to manage its investments may be adversely affected when shares are repeatedly bought, sold or exchanged in response to short-term market fluctuations — also known as “market timing.” The Funds are not designed for market timing organizations or other entities using programmed or frequent purchases and sales or exchanges. The exchange privilege is not intended as a vehicle for short-term trading. Excessive purchase and sale or exchange activity may interfere with portfolio management, increase expenses and taxes and may have an adverse effect on the performance of a Fund and its returns to shareholders. For example, large flows of cash into and out of a Fund may require the management team to allocate a significant amount of assets to cash or other short-term investments or sell securities, rather than maintaining such assets in securities selected to achieve the Fund’s investment objective. Frequent trading may cause a Fund to sell securities at less favorable prices, and transaction costs, such as brokerage commissions, can reduce a Fund’s performance.

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There is no assurance that the methods described above will prevent market timing or other trading that may be deemed abusive.

The Funds may from time to time use other methods that they believe are appropriate to deter market timing or other trading activity that may be detrimental to a Fund or long-term shareholders.

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Management of the Funds

BlackRock

BlackRock, each Fund’s investment adviser, manages each Fund’s investments and its business operations subject to the oversight of the Board of BlackRock Municipal Bond Fund, Inc. (the “Corporation”). While BlackRock is ultimately responsible for the management of the Funds, it is able to draw upon the trading, research and expertise of its asset management affiliates for portfolio decisions and management with respect to certain portfolio securities. BlackRock is an indirect, wholly-owned subsidiary of BlackRock, Inc.

High Yield Fund Total Annual Management Fee (Before Waivers)

With respect to the High Yield Fund, the annual management fees payable to BlackRock (as a percentage of average daily net assets) are calculated as follows:

Average Daily Net Assets	Rate of Management Fee
Not exceeding $1 billion	0.47%
In excess of $1 billion but not exceeding $3 billion	0.44%
In excess of $3 billion but not exceeding $5 billion	0.42%
In excess of $5 billion but not exceeding $10 billion	0.41%
In excess of $10 billion	0.40%

National Fund and Short-Term Fund Total Annual Management Fees (Before Waivers)

With respect to the National Fund and the Short-Term Fund, the annual management fees payable to BlackRock (as a percentage of average daily net assets) are calculated as follows:

	Rate of Management Fee
Aggregate average daily net assets of the two combined Funds¹	National Fund	Short-Term Fund
First $250 million	0.410%	0.360%
$250 million – $400 million	0.385%	0.340%
$400 million – $550 million	0.385%	0.320%
Greater than $550 million	0.385%	0.290%

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For the fiscal year ended June 30, 2019, the aggregate management fees, net of any applicable waivers, paid by each Fund to BlackRock as a percentage of each Fund’s average daily net assets were:

High Yield Fund	0.44%
National Fund	0.36%
Short-Term Fund	0.23%

BlackRock has agreed to cap net expenses (excluding (i) interest, taxes, dividends tied to short sales, brokerage commissions, and other expenditures which are capitalized in accordance with generally accepted accounting principles; (ii) expenses incurred directly or indirectly by a Fund as a result of investments in other investment companies and pooled investment vehicles; (iii) other expenses attributable to, and incurred as a result of, a Fund’s investments; and (iv) extraordinary expenses (including litigation expenses) not incurred in the ordinary course of a Fund’s business, if any) of Class K Shares of a Fund at the levels shown below and in a Fund’s fees and expenses table in the “Fund Overview” section of this prospectus. Items (i), (ii), (iii) and (iv) in the preceding sentence are referred to in this prospectus as “Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses.” To achieve these expense caps, BlackRock has agreed to waive and/or reimburse fees or expenses if these operating expenses exceed a certain limit.

	Contractual Caps¹ on Total Annual Fund Operating Expenses² (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses)
High Yield Fund
Class K Shares	0.49%
National Fund
Class K Shares	0.38%
Short-Term Fund
Class K Shares	0.31%

¹	The contractual caps are in effect through October 31, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of a Fund.

²	As a percentage of average daily net assets.

A discussion of the basis for the Board’s approval of each Management Agreement with BlackRock is included in each Fund’s annual shareholder report for the fiscal year ended June 30, 2019.

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BlackRock Mutual Funds Advisory Fee Litigation. In the lawsuit, which purports to be brought derivatively on behalf of Global Allocation and Equity Dividend, the plaintiffs allege that the Defendants violated Section 36(b) of the Investment Company Act by receiving allegedly excessive investment advisory fees from Global Allocation and Equity Dividend. On June 13, 2018, the court granted in part and denied in part the Defendants’ motion for summary judgment. On July 25, 2018, the plaintiffs served a pleading that supplemented the time period of their alleged damages to run through the date of trial. The lawsuit seeks, among other things, to recover on behalf of Global Allocation and Equity Dividend all allegedly excessive advisory fees received by the Defendants beginning twelve months preceding the start of the lawsuit with respect to each of Global Allocation and Equity Dividend and ending on the date of judgment, along with purported lost investment returns on those amounts, plus interest. The Defendants believe the claims in the lawsuit are without merit. The trial on the remaining issues was completed on August 29, 2018. On February 8, 2019, the court issued an order dismissing the claims in their entirety. On March 8, 2019, the plaintiffs provided notice that they are appealing both the February 8, 2019 post-trial order and the June 13, 2018 order partially granting Defendants’ motion for summary judgment.

Portfolio Manager Information

High Yield Fund

The Fund is managed by a team of financial professionals. Walter O’Connor, CFA, and Theodore Jaeckel, CFA, are jointly and primarily responsible for the day-to-day management of the Fund.

Portfolio Manager	Primary Role	Since	Title and Recent Biography
Walter O’Connor, CFA	Responsible for the day-to-day management of each Fund’s portfolio, including setting each Fund’s overall investment strategy and overseeing the management of each Fund.	2006	Managing Director of BlackRock, Inc. since 2006.
Theodore R. Jaeckel, CFA	Responsible for the day-to-day management of each Fund’s portfolio, including setting each Fund’s overall investment strategy and overseeing the management of each Fund.	2006	Managing Director of BlackRock, Inc. since 2006.

National Fund

The Fund is managed by a team of financial professionals. Walter O’Connor, CFA, and Michael Kalinoski, CFA, are jointly and primarily responsible for the day-to-day management of the Fund.

Portfolio Manager	Primary Role	Since	Title and Recent Biography
Walter O’Connor, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	1996	Managing Director of BlackRock, Inc. since 2006.
Michael Kalinoski, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	2016	Director of BlackRock, Inc. since 2006.

Short-Term Fund

The Fund is managed by a team of financial professionals. Kevin Schiatta, CFA, and Kristi Manidis are jointly and primarily responsible for the day-to-day management of the Fund.

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Portfolio Manager	Primary Role	Since	Title and Recent Biography
Kevin A. Schiatta, CFA	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	2016	Director of BlackRock, Inc. since 2006.
Kristi Manidis	Responsible for the day-to-day management of the Fund’s portfolio, including setting the Fund’s overall investment strategy and overseeing the management of the Fund.	2019	Director of BlackRock, Inc. since 2016; Vice President of BlackRock, Inc. from 2011 to 2015; Associate of BlackRock, Inc. from 2006 to 2010.

Conflicts of Interest

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one or more clients or BlackRock, its Affiliates or Entities or their directors, officers or employees, may have the effect of diluting or otherwise disadvantaging the values, prices or investment strategies of the Funds. The Funds’ activities may be limited because of regulatory restrictions applicable to BlackRock, one or more Affiliates or Entities and/or their internal policies designed to comply with such restrictions.

Under a securities lending program approved by the Board, the Corporation, on behalf of the Funds, has retained BlackRock Investment Management, LLC (“BIM”), an Affiliate of BlackRock, to serve as the securities lending agent for the Funds to the extent that the Funds participate in the securities lending program. For these services, the securities lending agent will receive a fee from a Fund, including a fee based on the returns earned on the Fund’s investment of the cash received as collateral for the loaned securities. In addition, one or more Affiliates or Entities may be among the entities to which the Funds may lend their portfolio securities under the securities lending program.

Valuation of Fund Investments

When you buy shares, you pay the net asset value. This is the offering price. Shares are also redeemed at their net asset value. Each Fund calculates the net asset value of each class of its shares each day the NYSE is open, generally as of the close of regular trading hours on the NYSE, based on prices at the time of closing. The NYSE generally closes at 4:00 p.m. (Eastern time). The net asset value used in determining your share price is the next one calculated after your purchase or redemption order is received.

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Dividends, Distributions and Taxes

BUYING A DIVIDEND

Each Fund will distribute net investment income, if any, monthly and net realized capital gain, if any, at least annually. Each Fund may also pay a special distribution at the end of the calendar year to comply with federal tax requirements. Dividends may be reinvested automatically in shares of each Fund at net asset value without a sales charge or may be taken in cash. If you would like to receive dividends in cash, contact your Financial Intermediary or the Fund. Although this cannot be predicted with any certainty, the Fund anticipates that a significant amount of its dividends, if any, will consist of capital gains. Capital gains may be taxable to you at different rates depending on how long the Fund held the assets sold.

Your tax consequences from an investment in the Fund will depend on whether you have invested through a qualified tax-exempt plan described in section 401(a) of the Internal Revenue Code (a “Qualified Plan”).

Investments Through a Qualified Plan

Special tax rules apply to investments made through Qualified Plans. If you are invested through a Qualified Plan (and Fund shares are not “debt-financed property” to the plan), then you will not be subject to U.S. federal income tax on the dividends paid by the Fund or the gain realized from a redemption or exchange of Fund shares until you withdraw or receive distributions from the plan. Distributions you receive from the Qualified Plan may be subject to U.S. federal withholding tax depending on the kind of payment you receive.

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Investments Not Made Through Qualified Plans

Each Fund intends to make income distributions, most of which will be excludable from gross income for federal tax purposes. Some distributions may be taxable.

The Fund will purchase a municipal security only if it is accompanied by an opinion of counsel to the issuer, which is delivered on the date of issuance of the security, that the interest paid on such security is excludable from gross income for Federal income tax purposes and exempt from New York State income taxes. For purposes of the Fund’s investment strategies, municipal securities and municipal bonds do not include certain tax credit bonds or tax subsidy bonds issued by municipalities and/or states, the interest of which is generally taxable for Federal income tax purposes. Holders of tax credit bonds may be entitled to be allocated income tax credits of certain amounts. To the extent that the dividends distributed by the Fund are derived from bond interest income that is excludable from gross income for Federal income tax purposes, they are exempt from Federal income tax.

There is a possibility that events occurring after the date of issuance of a security, or after the Fund’s acquisition of a security, may result in a determination that the interest on that security is, in fact, includable in gross income for Federal income tax purposes retroactively to its date of issue. Such a determination may cause a portion of prior distributions received by shareholders to be taxable to those shareholders in the year of receipt.

If you are not invested through a Qualified Plan, you will generally pay tax on dividends from the Fund whether you receive them in cash or additional shares. If you redeem Fund shares or exchange them for shares of another fund, you generally will be treated as having sold your shares and any gain on the transaction may be subject to tax. Fund distributions derived from qualified dividend income, which consists of dividends received from U.S. corporations and qualifying foreign corporations, and long-term capital gains, are eligible for taxation at a maximum rate of 15% or 20% for individuals, depending on whether their income exceeds certain threshold amounts, which are adjusted annually for inflation.

Special Considerations for Non-U.S. Persons

If you are not invested through a Qualified Plan and you are neither a tax resident nor a citizen of the United States or if you are a foreign entity (other than a pass-through entity to the extent owned by U.S. persons), the Fund’s ordinary income dividends will generally be subject to a 30% U.S. withholding tax, unless a lower treaty rate applies. However, certain distributions paid to a foreign shareholder and reported by the Fund as capital gain dividends, interest-related dividends or short-term capital gain dividends may be eligible for an exemption from U.S. withholding tax.

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Financial Highlights

The Financial Highlights table is intended to help you understand each Fund’s financial performance for the periods shown. Effective September 1, 2015 and August 15, 2016, the Board approved the reclassification of BlackRock Shares of Short-Term Fund and National Fund, respectively, as Class K Shares. Financial information for Class K Shares prior to September 1, 2015 (Short-Term Fund) and August 15, 2016 (National Fund), reflect the performance of the share classes when they were classified as BlackRock Shares. Certain information reflects the financial results for a single Fund share. The total returns in the tables represent the rate that an investor would have earned or lost on an investment in the indicated Fund (assuming reinvestment of all dividends and/or distributions). The information has been audited by Deloitte & Touche LLP, whose report, along with the indicated Fund’s financial statements, is included in each Fund’s Annual Report, which is available upon request.

Financial Highlights of BlackRock High Yield Municipal Fund

	Class K
(For a share outstanding throughout each period)	Year Ended 06/30/19	Period from 01/25/18^(a) to 06/30/18
Net asset value, beginning of period	$ 9.59	$ 9.62
Net investment income^(b)	0.39	0.18
Net realized and unrealized gain (loss)	0.30	(0.04)
Net increase from investment operations	0.69	0.14
Distributions from net investment income^(c)	(0.39)	(0.17)
Net asset value, end of period	$ 9.89	$ 9.59
Total Return^(d)
Based on net asset value	7.40%	1.50% ^(e)
Ratios to Average Net Assets^(f)
Total expenses	0.69%	0.67% ^(g)(h)
Total expenses after fees waived and/or reimbursed and paid indirectly	0.65%	0.62% ^(g)
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense, fees, and amortization of offering costs⁽ⁱ⁾	0.49%	0.49% ^(g)
Net investment income	4.04%	4.48% ^(g)
Supplemental Data
Net assets, end of period (000)	$49,062	$ 11,712
Borrowings outstanding, end of period (000)	$75,301	$ 61,022
Portfolio turnover rate	14%	25%

^(a)	Commencement of operations.
^(b)	Based on average Common Shares outstanding.
^(c)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(d)	Where applicable, assumes the reinvestment of distributions.
^(e)	Aggregate total return.

^(f)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended 06/30/19	Period from 01/25/18^(a) to 06/30/18
Investments in underlying funds	0.01%	0.01%

^(g)	Annualized.

^(h)	Offering costs were not annualized in the calculation of the expense ratios. If these expenses were annualized, the total expenses would have been 0.68%.
⁽ⁱ⁾	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (continued)

Financial Highlights of BlackRock National Municipal Fund

	Class K
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$ 10.79	$ 10.88	$ 11.22	$ 10.87	$ 10.88
Net investment income^(a)	0.33	0.33	0.35	0.36	0.39
Net realized and unrealized gain (loss)	0.28	(0.09)	(0.34)	0.35	(0.01)
Net increase from investment operations	0.61	0.24	0.01	0.71	0.38
Distributions from net investment income^(b)	(0.33)	(0.33)	(0.35)	(0.36)	(0.39)
Net asset value, end of year	$ 11.07	$ 10.79	$ 10.88	$ 11.22	$ 10.87
Total Return^(c)
Based on net asset value	5.82%	2.28%	0.15%	6.70%	3.53%
Ratios to Average Net Assets^(d)
Total expenses	0.46%	0.44%	0.48%	0.53%	0.58%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.43%	0.39%	0.41%	0.48%	0.49%
Total expenses after fees waived and/or reimbursed and paid indirectly and excluding interest expense and fees	0.38% ^(e)	0.39%	0.40% ^(e)	0.46% ^(e)	0.46% ^(e)
Net investment income	3.09%	3.09%	3.24%	3.24%	3.56%
Supplemental Data
Net assets, end of year (000)	$3,736,686	$3,012,495	$1,847,397	$332,000	$341,071
Borrowings outstanding, end of year (000)	$ 324,360	$ —	$ —	$ —	$275,550
Portfolio turnover rate	77%	51%	83%	83%	28%

^(a)	Based on average shares outstanding.
^(b)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(c)	Where applicable, assumes the reinvestment of distributions.

^(d)	Excludes expenses incurred indirectly as a result of investments in underlying funds as follows:

	Year Ended June 30,
	2019	2018	2017	2016	2015
Investments in underlying funds	0.01%	0.01%	0.01%	—%	—%

^(e)	Interest expense and fees relate to TOB Trusts. See Note 4 of the Notes to Financial Statements for details.

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Financial Highlights (concluded)

Financial Highlights of BlackRock Short-Term Municipal Fund

	Class K
	Year Ended June 30,
(For a share outstanding throughout each period)	2019	2018	2017	2016	2015
Net asset value, beginning of year	$10.08	$10.12	$ 10.18	$ 10.11	$10.15
Net investment income^(a)	0.14	0.08	0.00 ^(b)	0.05	0.02
Net realized and unrealized gain (loss)	0.10	—	0.01	0.06	(0.02)
Net increase from investment operations	0.24	0.08	0.01	0.11	—
Distributions ^(c)
From net investment income	(0.17)	(0.12)	(0.07)	(0.04)	(0.04)
From net realized gain	—	—	(0.00) ^(d)	(0.00) ^(d)	—
Total distributions	(0.17)	(0.12)	(0.07)	(0.04)	(0.04)
Net asset value, end of year	$10.15	$10.08	$ 10.12	$ 10.18	$10.11
Total Return^(e)
Based on net asset value	2.37%	0.76%	0.13%	1.13%	(0.01)%
Ratios to Average Net Assets
Total expenses	0.38%	0.38%	0.43%	0.42%	0.41%
Total expenses after fees waived and/or reimbursed and paid indirectly	0.31%	0.31%	0.34%	0.42%	0.40%
Net investment income	1.43%	0.75%	0.02%	0.45%	0.21%
Supplemental Data
Net assets, end of year (000)	$7,450	$6,719	$ 3,238	$ 3,279	$6,732
Portfolio turnover rate	129%	153%	88%	67%	72%

^(a)	Based on average shares outstanding.
^(b)	Amount is less than $0.005 per share.
^(c)	Distributions for annual periods determined in accordance with U.S. federal income tax regulations.
^(d)	Amount is greater than $(0.005) per share.
^(e)	Where applicable, assumes the reinvestment of distributions.

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