August 28, 2020

 

PROSPECTUS

 

MFS® Corporate Bond Fund

 

The investment objective of the fund is to seek total return with an emphasis on current income, but also considering capital appreciation.

 

CLASS		TICKER SYMBOL
Class A		MFBFX
Class B		MFBBX
Class C		MFBCX
Class I		MBDIX
Class R1		MFBGX
Class R2		MBRRX
Class R3		MFBHX
Class R4		MFBJX
Class R6		MFBKX

 

Beginning on January 1, 2021, as permitted by regulations adopted by the U.S. Securities and Exchange Commission, paper copies of the fund’s annual and semiannual shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports.  Instead, the complete reports will be made available on the fund’s website (funds.mfs.com), and you will be notified by mail each time a report is posted and provided with a website link to access the report.

 

If you are already signed up to receive shareholder reports by email, you will not be affected by this change and you need not take any action.  You may sign up to receive shareholder reports and other communications from the fund by email by contacting your financial intermediary (such as a broker-dealer or bank) or, if you hold your shares directly with the fund, by calling 1-800-225-2606 or by logging on to MFS Access at mfs.com.

 

Beginning on January 1, 2019, you may elect to receive all future reports in paper free of charge.  Contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports.  If you invest directly with the fund, you can call 1-800-225-2606 or send an email request to orderliterature@mfs.com to let the fund know that you wish to continue receiving paper copies of your shareholder reports.  Your election to receive reports in paper will apply to all funds held in your account if you invest through your financial intermediary or all funds held with the MFS fund complex if you invest directly.

 

Table of contents

 

SUMMARY OF KEY INFORMATION	2
INVESTMENT OBJECTIVE, STRATEGIES, AND RISKS	5
MANAGEMENT OF THE FUND	8
DESCRIPTION OF SHARE CLASSES	9
HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES	12
OTHER INFORMATION	16
FINANCIAL HIGHLIGHTS	18
APPENDIX A – WAIVERS AND REDUCTIONS OF SALES CHARGES	A-1

 

The Securities and Exchange Commission has not approved or disapproved the fund’s shares or determined whether this prospectus is accurate or complete. Anyone who tells you otherwise is committing a crime.

 

MFB-PRO-082820

 

 

MFS Corporate Bond Fund

 

Summary of Key Information

 

Investment Objective

 

The fund’s investment objective is to seek total return with an emphasis on current income, but also considering capital appreciation.

 

Fees and Expenses

 

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy and hold shares of the fund, which are not reflected below.

 

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 10 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

 

Shareholder Fees (fees paid directly from your investment):

 

Share Class

A

B

C

I

R1

R2

R3

R4

R6

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

4.25

%

None

None

None

None

None

None

None

None

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

1.00

%#

4.00

%

1.00

%

None

None

None

None

None

None

 

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MFS Corporate Bond Fund

 

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

 

Share Class		A		B		C		I		R1		R2		R3		R4		R6
Management Fee		0.38	%	0.38	%	0.38	%	0.38	%	0.38	%	0.38	%	0.38	%	0.38	%	0.38	%
Distribution and/or Service (12b-1) Fees		0.25	%	1.00	%	1.00	%	None		1.00	%	0.50	%	0.25	%	None		None
Other Expenses		0.15	%	0.15	%	0.15	%	0.15	%	0.15	%	0.15	%	0.15	%	0.15	%	0.05	%
Total Annual Fund Operating Expenses		0.78	%	1.53	%	1.53	%	0.53	%	1.53	%	1.03	%	0.78	%	0.53	%	0.43	%

 

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#                 This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.

 

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 you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

 

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

 

		1 YEAR			3 YEARS			5 YEARS			10 YEARS
Class A Shares		$	501		$	664		$	840		$	1,350
Class B Shares assuming
redemption at end of period		$	556		$	783		$	1,034		$	1,621
no redemption at end of period		$	156		$	483		$	834		$	1,621
Class C Shares assuming
redemption at end of period		$	256		$	483		$	834		$	1,824
no redemption at end of period		$	156		$	483		$	834		$	1,824
Class I Shares		$	54		$	170		$	296		$	665
Class R1 Shares		$	156		$	483		$	834		$	1,824
Class R2 Shares		$	105		$	328		$	569		$	1,259
Class R3 Shares		$	80		$	249		$	433		$	966
Class R4 Shares		$	54		$	170		$	296		$	665
Class R6 Shares		$	44		$	138		$	241		$	542

 

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 transaction 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 36% of the average value of its portfolio.

 

Principal Investment Strategies

 

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in corporate debt instruments. MFS may also invest the fund’s assets in U.S. Government securities.

 

MFS invests the majority of the fund’s assets in investment grade quality debt instruments, but may also invest in below investment grade quality debt instruments.

 

MFS may invest the fund’s assets in foreign securities.

 

MFS normally invests the fund’s assets across different industries and sectors, but MFS may invest a significant percentage of the fund’s assets in issuers in a single industry or sector.

 

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, swaps, and certain complex structured securities.

 

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative screening tools that systematically evaluate instruments may also be considered. In structuring the fund, MFS also considers top-down factors.

 

For purposes of the fund’s 80% policy, net assets include the amount of any borrowings for investment purposes.

 

Principal Risks

 

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

 

The principal risks of investing in the fund are:

 

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

 

Debt Market Risk:  Debt markets can be volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single instrument, issuer, or borrower, a particular type of instrument, issuer, or borrower, a segment of the debt markets or the debt markets generally. Certain events can have

 

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MFS Corporate Bond Fund

 

a dramatic adverse effect on debt markets and may lead to periods of high volatility and reduced liquidity in a debt market or segment of a debt market.

 

Interest Rate Risk:  In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities, or that do not pay current interest.

 

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or other entity responsible for payment, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in, or perceptions of, the financial condition of the issuer, borrower, counterparty, or other entity, or underlying collateral or assets, or changes in, or perceptions of, specific or general market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.

 

Below investment grade quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Below investment grade quality debt instruments are regarded as having predominantly speculative characteristics. Below investment grade quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

 

Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging and frontier markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

 

Focus Risk:  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the fund is exposed.

 

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

 

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

 

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

 

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability or willingness to perform in accordance with the terms of the transaction.

 

Liquidity Risk:  It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

 

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares.  These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices.  Redemptions of a large number of shares also may increase transaction costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities.

 

Performance Information

 

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

 

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

 

Class A Bar Chart.  The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.

 

 

The total return for the six-month period ended June 30, 2020, was 5.87%. During the period(s) shown in the bar chart, the highest quarterly return was 5.53% (for the calendar quarter ended March 31, 2019) and the lowest quarterly return was (2.94)% (for the calendar quarter ended June 30, 2013).

 

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MFS Corporate Bond Fund

 

Performance Table.

 

Average Annual Total Returns

(For the Periods Ended December 31, 2019)

 

Share Class		1 YEAR		5 YEARS		10 YEARS
Returns Before Taxes
B Shares		9.60	%	3.25	%	4.84	%
C Shares		12.53	%	3.58	%	4.68	%
I Shares		14.70	%	4.61	%	5.72	%
R1 Shares		13.52	%	3.58	%	4.68	%
R2 Shares		14.13	%	4.11	%	5.20	%
R3 Shares		14.41	%	4.37	%	5.46	%
R4 Shares		14.61	%	4.61	%	5.72	%
R6 Shares		14.81	%	4.72	%	5.80	%
A Shares		9.55	%	3.47	%	5.00	%
Returns After Taxes on Distributions
A Shares		8.18	%	2.06	%	3.42	%
Returns After Taxes on Distributions and Sale of Fund Shares
A Shares		5.62	%	2.00	%	3.19	%
Index Comparison (Reflects no deduction for fees, expenses, or taxes)
Bloomberg Barclays U.S. Credit Bond Index		13.80	%	4.39	%	5.32	%

 

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. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

 

Investment Adviser                                                                                                                 

 

MFS serves as the investment adviser for the fund.

 

Portfolio Manager(s)

 

Portfolio Manager		Since		Title
Alexander Mackey		2017		Investment Officer of MFS
Henry Peabody		December 2019		Investment Officer of MFS
Robert Persons		2005		Investment Officer of MFS

 

Effective June 30, 2021, Robert Persons will no longer be a portfolio manager of the fund.

 

Purchase and Sale of Fund Shares

 

You may purchase and redeem shares of the fund each day the New York Stock Exchange (the NYSE) is open for trading. You may purchase or redeem shares either by having your financial intermediary process your purchase or redemption, or through MFS Service Center, Inc. (MFSC) by overnight mail (MFSC, Suite 219341, 430 W 7th Street, Kansas City, MO 64105-1407), by mail ([Fund Name], P.O. Box 219341, Kansas City, MO 64121-9341), by telephone (1-800-225-2606), or via the Internet at mfs.com (MFS Access).

 

The fund’s initial and subsequent investment minimums generally are as follows:

 

Class		Initial Minimum		Subsequent Minimum
Class A, Class B, Class C		None – automatic investment plans and certain asset-based fee programs $25 – employer-sponsored retirement plans $250 – Traditional and Roth IRAs $1,000 – other accounts		$50 – by check and non-systematic written exchange request, and via MFSC telephone representatives None – other purchases
Class I, Class R1, Class R2, Class R3, Class R4, Class R6		None		None

 

Purchases of Class B shares are closed to new and existing investors except through reinvestment of dividends and capital gain distributions. Existing investors may continue to exchange their Class B shares for the same share class of another MFS fund.

 

Taxes

 

If your shares are held in a taxable account, the fund’s distributions will be taxed to you as ordinary income and/or capital gains.  If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

 

Payments to Broker/Dealers and Other Financial Intermediaries

 

If you purchase shares of the fund through a broker/dealer or other financial intermediary (such as a bank), the fund, MFS, and/or MFS’ affiliates may pay the financial intermediary for the sale of shares of a fund and/or the servicing of shareholder accounts. These payments may create a conflict of interest by influencing your broker/dealer or other financial intermediary and your salesperson to recommend the fund over another investment. Ask your financial intermediary or visit your financial intermediary’s website for more information.

 

Investment Objective, Strategies, and Risks

 

Investment Objective

 

The fund’s investment objective is to seek total return with an emphasis on current income, but also considering capital appreciation. The fund’s objective may be changed without shareholder approval.

 

Principal Investment Strategies

 

MFS normally invests at least 80% of the fund’s net assets in corporate debt instruments. MFS may also invest the fund’s assets in U.S. Government securities.

 

MFS invests the majority of the fund’s assets in investment grade quality debt instruments, but may also invest in below investment grade quality debt instruments.

 

MFS may invest the fund’s assets in foreign securities.

 

MFS normally invests the fund’s assets across different industries and sectors, but MFS may invest a significant percentage of the fund’s assets in issuers in a single industry or sector.

 

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market,

 

5

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MFS Corporate Bond Fund

 

segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments.

 

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers in light of the issuers’ financial condition and market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality and terms, any underlying assets and their credit quality, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. MFS may also consider environmental, social, and governance (ESG) factors in its fundamental investment analysis. Quantitative screening tools that systematically evaluate the structure of a debt instrument and its features may also be considered. In structuring the fund, MFS also considers top-down factors, including sector allocations, yield curve positioning, duration, macroeconomic factors, and risk management factors.

 

For purposes of the fund’s 80% policy, net assets include the amount of any borrowings for investment purposes.

 

Principal Investment Types

 

The principal investment types in which the fund may invest are:

 

Debt Instruments: Debt instruments represent obligations of corporations, governments, and other entities to repay money borrowed, or other instruments believed to have debt-like characteristics. The issuer or borrower usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the instrument. Debt instruments generally trade in the over-the-counter market and can be less liquid than other types of investments, particularly during adverse market and economic conditions.  During certain market conditions, debt instruments in some or many segments of the debt market can trade at a negative interest rate (i.e., the price to purchase the debt instrument is more than the present value of expected interest payments and principal due at the maturity of the instrument). Some debt instruments, such as zero coupon bonds or payment-in-kind bonds, do not pay current interest. Other debt instruments, such as certain mortgage-backed securities and other securitized instruments, make periodic payments of interest and/or principal. Some debt instruments are partially or fully secured by collateral supporting the payment of interest and principal.

 

Corporate Bonds:  Corporate bonds are debt instruments issued by corporations or similar entities.

 

U.S. Government Securities:  U.S. Government securities are securities issued or guaranteed as to the payment of principal and interest by the U.S. Treasury, by an agency or instrumentality of the U.S. Government, or by a U.S. Government-sponsored entity. Certain U.S. Government securities are not supported as to the payment of principal and interest by the full faith and credit of the U.S. Treasury or the ability to borrow from the U.S. Treasury. Some U.S. Government securities are supported as to the payment of principal and interest only by the credit of the entity issuing or guaranteeing the security. U.S. Government securities include mortgage-backed securities and other types of securitized instruments guaranteed by the U.S. Treasury, by an agency or instrumentality of the U.S. Government, or by a U.S. Government-sponsored entity.

 

Derivatives:  Derivatives are financial contracts whose value is based on the value of one or more underlying indicators or the difference between underlying indicators. Underlying indicators may include a security or other financial instrument, asset, currency, interest rate, credit rating, commodity, volatility measure, or index. Derivatives often involve a counterparty to the transaction. Derivatives include futures, forward contracts, options, swaps, and certain complex structured securities.

 

Principal Risks

 

The yield and share price of the fund will change daily based on changes in interest rates and market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. The significance of any specific risk to an investment in the fund will vary over time depending on the composition of the fund’s portfolio, market conditions, and other factors. You should read all of the risk information below carefully, because any one or more of these risks may result in losses to the fund.

 

The principal risks of investing in the fund are:

 

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. In addition, MFS or the fund’s other service providers may experience disruptions or operating errors that could negatively impact the fund.

 

Debt Market Risk:  Debt markets can be volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single instrument, issuer, or borrower, a particular type of instrument, issuer, or borrower, a segment of the debt markets, or debt markets generally.  Certain changes or events, such as political, social, or economic developments, including increasing and negative interest rates or the U.S. government’s inability at times to agree on a long-term budget and deficit reduction plan (which has in the past resulted and may in the future result in a government shutdown); market closures and/or trading halts; government or regulatory actions, including the imposition of tariffs or other protectionist actions and changes in fiscal, monetary, or tax policies; natural disasters; outbreaks of pandemic and epidemic diseases; terrorist attacks; war; and other geopolitical changes or events can have a dramatic adverse effect on debt markets and may lead to periods of high volatility and reduced liquidity in a debt market or a segment of a debt market.

 

Interest Rate Risk:  The price of a debt instrument typically changes in response to interest rate changes. Interest rates can change in response to the supply and demand for credit, government and/or central bank monetary policy and action, inflation rates, and other factors. In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities, or that do not pay current interest. In addition, short-term and long-term interest rates, and interest rates in different countries, do not necessarily move in the same direction or by the same amount. An instrument’s reaction to interest rate changes depends on the timing of its interest and principal payments and the current interest rate for each of those time periods. Instruments with floating interest rates can be less sensitive to interest rate changes. The price of an instrument trading at a negative interest rate responds to interest rate changes like other debt instruments; however, an instrument purchased at a negative interest rate is expected to produce a negative return if held to maturity. Changes in government and/or central bank monetary policy may affect the level of interest rates.

 

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MFS Corporate Bond Fund

 

Credit Risk:  The price of a debt instrument depends, in part, on the issuer’s or borrower’s credit quality or ability to pay principal and interest when due. The price of a debt instrument is likely to fall if an issuer or borrower defaults on its obligation to pay principal or interest, if the instrument’s credit rating is downgraded by a credit rating agency, or based on other changes in, or perceptions of, the financial condition of the issuer or borrower.  For certain types of instruments, including derivatives, the price of the instrument depends in part on the credit quality of the counterparty to the transaction. For other types of debt instruments, including securitized instruments, the price of the debt instrument also depends on the credit quality and adequacy of the underlying assets or collateral as well as whether there is a security interest in the underlying assets or collateral. Enforcing rights, if any, against the underlying assets or collateral may be difficult.

 

Below investment grade quality debt instruments can involve a substantially greater risk of default or can already be in default, and their values can decline significantly over short periods of time. Below investment grade quality debt instruments are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and principal. Below investment grade quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments. The market for below investment grade quality debt instruments can be less liquid, especially during periods of recession or general market decline.

 

Foreign Risk:  Investments in securities of foreign issuers, securities of companies with significant foreign exposure, and foreign currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. Political, social, diplomatic, and economic developments, U.S. and foreign government action such as the imposition of currency or capital blockages, controls, or tariffs, economic and trade sanctions or embargoes, security suspensions, entering or exiting trade or other intergovernmental agreements, or the expropriation or nationalization of assets in a particular country, can cause dramatic declines in certain or all securities with exposure to that country and other countries. In the event of nationalization, expropriation, or other confiscation, the fund could lose its entire foreign investment in a particular country. Economies and financial markets are interconnected, which increases the likelihood that conditions in one country or region can adversely impact issuers in different countries and regions. Less stringent regulatory, accounting, auditing, and disclosure requirements for issuers and markets are more common in certain foreign countries. Enforcing legal rights can be difficult, costly, and slow in certain foreign countries, and can be particularly difficult against foreign governments. Changes in currency exchange rates can significantly impact the financial condition of a company or other issuer with exposure to multiple countries as well as affect the U.S. dollar value of foreign currency investments and investments denominated in foreign currencies. Additional risks of foreign investments include trading, settlement, custodial, and other operational risks, and withholding and other taxes. These factors can make foreign investments, especially those tied economically to emerging and frontier markets (emerging markets that are early in their development), more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions than the U.S. market.

 

Focus Risk:  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions include business environment changes; economic factors such as fiscal, monetary, and tax policies; inflation and unemployment rates; and government and regulatory changes.  The fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the fund is exposed.

 

Prepayment/Extension Risk:  Many types of debt instruments, including mortgage-backed securities, securitized instruments, certain corporate bonds, and municipal housing bonds, and certain derivatives, are subject to the risk of prepayment and/or extension. Prepayment occurs when unscheduled payments of principal are made or the instrument is called or redeemed prior to an instrument’s maturity. When interest rates decline, the instrument is called, or for other reasons, these debt instruments may be repaid more quickly than expected. As a result, the holder of the debt instrument may not be able to reinvest the proceeds at the same interest rate or on the same terms, reducing the potential for gain. When interest rates increase or for other reasons, these debt instruments may be repaid more slowly than expected, increasing the potential for loss. In addition, prepayment rates are difficult to predict and the potential impact of prepayment on the price of a debt instrument depends on the terms of the instrument.

 

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to, and potentially greater than, the risks of the underlying indicator(s). Gains or losses from derivatives can be substantially greater than the derivatives’ original cost and can sometimes be unlimited.  Derivatives can involve leverage. Derivatives can be complex instruments and can involve analysis and processing that differs from that required for other investment types used by the fund. If the value of a derivative does not change as expected relative to the value of the market or other indicator to which the derivative is intended to provide exposure, the derivative may not have the effect intended. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments.

 

Leveraging Risk:  Certain transactions and investment strategies can result in leverage. Leverage involves investment exposure in an amount exceeding the initial investment. In transactions involving leverage, a relatively small change in an underlying indicator can lead to significantly larger losses to the fund. Leverage can cause increased volatility by magnifying gains or losses.

 

Counterparty and Third Party Risk:  Transactions involving a counterparty other than the issuer of the instrument, including clearing organizations, or a third party responsible for servicing the instrument or effecting the transaction, are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability or willingness to perform in accordance with the terms of the transaction.  If a counterparty or third party fails to meet its contractual obligations, goes bankrupt, or otherwise experiences a business interruption, the fund could miss investment opportunities, lose value on its investments, or otherwise hold investments it would prefer to sell, resulting in losses for the fund.

 

Liquidity Risk:  Certain investments and types of investments are subject to restrictions on resale, may trade in the over-the-counter market, or may not have an active trading market due to adverse market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, including investors trying to sell large quantities of a particular investment or type of investment, or lack of market makers or other buyers for a particular investment or type of investment.  At times, all or a significant portion of a market may not have an active trading market. Without an active trading market, it may be difficult to value, and it may not be possible to sell, these investments and the

 

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MFS Corporate Bond Fund

 

fund could miss other investment opportunities and hold investments it would prefer to sell, resulting in losses for the fund.  In addition, the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs, which could result in dilution of remaining investors’ interests in the fund.  The prices of illiquid securities may be more volatile than more liquid investments.

 

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares.  These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices.  While it is impossible to predict the overall impact of these transactions over time, there could be adverse effects on the fund’s performance to the extent that the fund may be required to sell securities or invest cash at times it would not otherwise do so.  Redemptions of a large number of shares also may increase transaction costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities.  In addition, a large redemption could result in the fund’s current expenses being allocated over a smaller asset base, leading to an increase in the fund’s expense ratio.

 

Other Investment Strategies and Risks

 

Active and Frequent Trading:  MFS may engage in active and frequent trading in pursuing the fund’s principal investment strategies. Frequent trading increases transaction costs, which can reduce the fund’s return. Frequent trading can also increase the possibility of capital gain distributions. Capital gain distributions generally increase your tax liability unless you hold your shares through a tax-advantaged or exempt vehicle.

 

Temporary Defensive Strategy:  In response to adverse market, economic, industry, political, or other conditions, MFS may depart from the fund’s principal investment strategies by temporarily investing for defensive purposes. When MFS invests defensively, different factors could affect the fund’s performance and the fund may not achieve its investment objective. In addition, the defensive strategy may not work as intended.

 

Further Information on Investment Strategies, Types, and Risks:  Information about investment strategies and investment types not described in the prospectus and the risks associated with those investment strategies and investment types are described in the fund’s Statement of Additional Information (SAI).

 

Management of the Fund

 

Investment Adviser

 

MFS, located at 111 Huntington Avenue, Boston, Massachusetts 02199, serves as the investment adviser for the fund.  Subject to the supervision of the fund’s Board of Trustees, MFS is responsible for managing the fund’s investments, executing transactions, and providing related administrative services and facilities under an Investment Advisory Agreement between the fund and MFS.

 

For the fiscal year ended April 30, 2020, the fund paid MFS an effective management fee equal to 0.37% of the fund’s average daily net assets.

 

The management fee set forth in the Investment Advisory Agreement is 0.39% of the fund’s average daily net assets annually of the first $1.1 billion; 0.38% of the fund’s average daily net assets annually in excess of $1.1 billion and up to $5 billion; 0.35% of the fund’s average daily net assets annually in excess of $5 billion and up to $10 billion; and 0.34% of the fund’s average daily net assets annually in excess of $10 billion.

 

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the fiscal year ended April 30, 2020, this management fee reduction amounted to 0.01% of the fund’s average daily net assets.

 

A discussion regarding the basis for the Board of Trustees’ approval of the Investment Advisory Agreement is available in the fund’s semi-annual report for the six-month period ended October 31, 2019.

 

MFS is America’s oldest mutual fund organization. MFS and its predecessor organizations have a history of money management dating from 1924 and the founding of the first mutual fund, Massachusetts Investors Trust. Net assets under the management of the MFS organization were approximately $507 billion as of June 30, 2020.

 

Disclosure of Portfolio Holdings. The fund has established a policy with respect to the disclosure of fund portfolio holdings. A description of this policy is provided in the SAI.

 

The following information is generally available to you at mfs.com/openendfunds by choosing the fund’s name:

 

Information		Approximate Date of Posting
Fund’s top 10 holdings as of each month’s end		11 days after month end
Fund’s full holdings as of each month’s end		19 days after month end

 

Holdings also include short positions, if any. Top 10 holdings exclude cash, cash equivalents, short-term investments, currency derivatives, and the cash portion of other derivatives. For purposes of full holdings, cash, cash equivalents, and short-term investments are aggregated and currency derivatives and the cash portion of other derivatives are aggregated.

 

Note that the fund or MFS may suspend the posting of this information or modify the elements of this Web posting policy without notice to shareholders. Once posted, the above information will generally remain available on mfs.com until at least the date on which the fund files a Form N-CSR or Form N-PORT for the period that includes the date as of which the mfs.com information is current.

 

Portfolio Manager(s)

 

Information regarding the portfolio manager(s) of the fund is set forth below. Further information regarding the portfolio manager(s), including other accounts managed, compensation, ownership of fund shares, and possible conflicts of interest, is available in the fund’s SAI.

 

Portfolio Manager		Primary Role		Five Year History
Alexander Mackey		Portfolio Manager		Employed in the investment area of MFS since 2001
Henry Peabody		Portfolio Manager		Employed in the investment area of MFS since July 2019; Vice President/Portfolio Manager at Eaton Vance Management prior to July 2019
Robert Persons		Portfolio Manager		Employed in the investment area of MFS since 2000

 

Effective June 30, 2021, Robert Persons will no longer be a portfolio manager of the fund.

 

Administrator

 

MFS provides the fund with certain financial, legal, and other administrative services under a Master Administrative Services

 

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MFS Corporate Bond Fund

 

Agreement between the fund and MFS. Under the Agreement, MFS is paid an annual fee for providing these services.

 

Distributor

 

MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, is the distributor of shares of the fund.

 

Shareholder Servicing Agent

 

MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, provides dividend and distribution disbursing and transfer agent and recordkeeping functions in connection with the issuance, transfer, and redemption of each class of shares of the fund under a Shareholder Servicing Agent Agreement. MFSC receives a fee based on the costs it incurs in providing these services and a target profit margin. In addition, MFSC is reimbursed for payments made to service providers that provide certain sub-accounting and other shareholder services (shareholder servicing payments) and its out-of-pocket expenses. No shareholder servicing payments are made for Class R6 shares.

 

Description of Share Classes

 

The fund offers Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, Class R4, and Class R6 shares through this prospectus. All classes of the fund have the same investment objective and investments, but each class has its own sales charge and expense structure. Your financial intermediary may also charge you additional fees, commissions, or other charges. You should consult with your financial intermediary to help you determine which class is most appropriate for you.

 

Purchases of Class B shares are closed to new and existing investors except through reinvestment of dividends and capital gain distributions. Existing investors may continue to exchange their Class B shares for the same share class of another MFS fund.

 

Share Class Eligibility

 

Your financial intermediary is responsible for determining if you meet any share class eligibility requirements. MFS does not generally monitor any share class eligibility requirements.

 

Class A, Class B, and Class C shares do not have any share class eligibility requirements.

 

Class I shares generally are available only to the following eligible investors:

 

●                  certain retirement plans established for the benefit of employees and former employees of MFS or its affiliates;

 

●                  defined benefit retirement plans, endowments or foundations;

 

●                  bank trust departments or law firms acting as trustee or manager for trust accounts;

 

●                  investors who purchase shares through asset-based fee programs available through financial intermediaries;

 

●                  employees and former employees of MFS and its subsidiaries who were employed by MFS or its subsidiaries on or after January 1, 2013, trusts, pension, profit-sharing or other retirement plans for the sole benefit of such persons, and joint accounts with such persons’ spouses or legal equivalents under applicable state law; and

 

●                  trustees and former trustees of any investment company for which MFD serves as a distributor and who served as trustee on or after January 1, 2013, trusts, pension, profit-sharing or other retirement plans for the sole benefit of such persons, and joint accounts with such persons’ spouses or legal equivalents under applicable state law.

 

Class I shares are also available to other institutional investors who have entered into an agreement with MFD to purchase Class I shares and investors who purchase shares through brokerage programs of certain financial intermediaries that have entered into an agreement with MFD to offer Class I shares through such programs. In addition, Class I shares are also available to investors whose Class A, Class B, or Class C shares have been converted to Class I shares as a result of no financial intermediary being specified on the investor’s account.  (Please see “Conversion Among Share Classes” below.)

 

Class R1, Class R2, Class R3, and Class R4 shares generally are available only to eligible retirement plans (401(k) plans, 457 plans, employer-sponsored 403(b) plans, profit sharing and money purchase pension plans, defined benefit plans and non-qualified deferred compensation plans any of whose accounts are maintained by the fund at an omnibus level (“Employer Retirement Plans”)), and health savings accounts under Section 223 of the Internal Revenue Code if such accounts are maintained by the fund at an omnibus level.

 

Class R1, Class R2, Class R3, and Class R4 shares generally are not available to traditional and Roth IRAs, Coverdell Educational Savings Accounts, SEPs, SAR-SEPs, SIMPLE IRAs, salary reduction only 403(b) plans, and Section 529 tuition plans.

 

Class R6 shares generally are available only to the following eligible investors:

 

●                  Employer Retirement Plans;

 

●                  health savings accounts under Section 223 of the Internal Revenue Code if such accounts are maintained by the fund at an omnibus level;

 

●                  investment companies distributed by MFD;

 

●                  endowments and foundations, local, city and state agencies (or entities acting on their behalf);

 

●                  funded welfare benefit plans (e.g., Voluntary Employees’ Beneficiary Association (VEBA) and Other Post-Employment (OPEB) plans);

 

●                  unaffiliated registered investment companies;

 

●                  collective investment trusts; and

 

●                  investors who purchase shares through asset-based fee programs of certain financial intermediaries that have entered into an agreement with MFD to offer Class R6 shares through such programs.

 

Class R6 shares are also available to other institutional investors who have entered into an agreement with MFD to purchase Class R6 shares and investors who purchase shares through brokerage programs of certain financial intermediaries that have entered into an agreement with MFD to offer Class R6 shares through such programs.

 

Conversion Among Share Classes

 

If you hold Class B shares for approximately eight years, they will convert to Class A shares of the fund. For purposes of calculating the conversion date, purchases made on any day during a calendar month will age one month at the close of business on the last day of that month, and at the close of business on the last day of each subsequent month.

 

All Class B shares you acquire through the reinvestment of dividends and distributions will be held in a separate sub-account. Each time any Class B shares in your account convert to Class A

 

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MFS Corporate Bond Fund

 

shares, a proportionate number of the Class B shares in the sub-account will also convert to Class A shares.

 

For shareholders invested in Class B shares through a financial intermediary, it is the responsibility of the financial intermediary to ensure that the investor is credited with the proper holding period. The automatic conversion of Class B shares to Class A shares will not apply to shares held through financial intermediaries that do not track the length of time that a shareholder has held such shares. Please consult your financial intermediary for more information.

 

If you hold Class C shares for approximately ten years, they will convert to Class A shares of the fund. For purposes of calculating the conversion date, purchases made on any day during a calendar month will age one month at the close of business on the last day of that month, and at the close of business on the last day of each subsequent month.

 

All Class C shares you acquire through the reinvestment of dividends and distributions will be held in a separate sub-account. Each time any Class C shares in your account convert to Class A shares, a proportionate number of the Class C shares in the sub-account will also convert to Class A shares.

 

For shareholders invested in Class C shares through a financial intermediary, it is the responsibility of the financial intermediary to ensure that the investor is credited with the proper holding period. The automatic conversion of Class C shares to Class A shares will not apply to shares held through financial intermediaries that do not track the length of time that a shareholder has held such shares. Please consult your financial intermediary for more information.

 

Shareholders may be able to convert between Class A shares and Class I shares of the fund if they satisfy eligibility requirements for the other class, if any.  Class I shareholders may be able to convert their Class I shares to Class R6 shares of the fund if they satisfy eligibility requirements of Class R6 shares.

 

Class C shareholders of the fund may be able to convert their shares to Class A shares of the fund if their financial intermediary provides written notification to MFD prior to such conversion that the intermediary has determined that Class A was the appropriate share class at the time of purchase for such shareholder and receives approval of such conversion by MFD.  Class C shareholders also may be able to convert their Class C shares not subject to a CDSC to Class I shares of the fund if they satisfy eligibility requirements of Class I shares.

 

Class A, Class B, or Class C shares in an account held directly with MFSC for which no financial intermediary is specified will be periodically converted to Class I shares as authorized by MFD.  If your Class A, Class B, or Class C shares are converted to Class I shares pursuant to this conversion feature, all future purchases in your account will be invested in Class I shares.  Shareholders will generally be provided with written notice at least 30 days prior to a conversion of their Class A, Class B, or Class C shares to Class I shares.

 

If a shareholder converts from one share class to another share class of the fund, as described above, the transaction will be based on the respective net asset value of each class as of the trade date for the conversion. Consequently, the converting shareholder may receive fewer shares or more shares than originally owned, depending on that day’s net asset values. The total value of the initially held shares, however, will equal the total value of the converted shares received. A conversion between share classes in the same fund, as described above, is a nontaxable event for federal income tax purposes.

 

Sales Charges and Waivers and Reductions

 

You may be subject to an initial sales charge when you purchase Class A shares, or a CDSC when you redeem Class A, Class B, or Class C shares. These sales charges are paid to MFD.

 

You may qualify for a sales charge waiver or reduction when you purchase or redeem shares. The waivers or reductions that are applicable to your transaction depend on your financial intermediary and the type of account and transaction.  Further details regarding these waivers and reductions are provided in Appendix A of this prospectus.  It is your responsibility to inform your financial intermediary or MFSC upon purchasing fund shares of your eligibility for a sales charge waiver or reduction. Waivers or reductions may be eliminated, modified, and added at any time without providing advance notice to shareholders.

 

Class A Shares.  You may purchase Class A shares at the offering price (which includes the applicable initial sales charge).

 

The amount of the initial sales charge you pay when you buy Class A shares differs depending upon the amount you invest, as follows:

 

		INITIAL SALES CHARGE AS PERCENTAGE OF:
Amount of Purchase		GROSS PURCHASE AMOUNT (OFFERING PRICE*)		NET AMOUNT INVESTED
Less than $100,000		4.25	%	4.44	%
$100,000 but less than $250,000		3.25	%	3.36	%
$250,000 but less than $500,000		2.25	%	2.30	%
$500,000 or more		None		None

 

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*                 Offering price is calculated by dividing the net asset value of a share by the difference between 1 and the initial sales charge percentage. Because the offering price is rounded to two decimal places, actual sales charges you pay may be more or less than those calculated using these percentages.

 

You may purchase Class A shares without an initial sales charge when you invest $500,000 or more in Class A shares. However, for purchasers other than Employer Retirement Plans, a CDSC of 1% will generally be deducted from your redemption proceeds if you redeem within 18 months of purchase.

 

Class B Shares.  You may purchase Class B shares at net asset value without an initial sales charge, but if you redeem your shares within the first six years after purchase, you may be subject to a CDSC (declining from 4% during the first year to 0% after six years).

 

The CDSC is imposed according to the following schedule:

 

Year of redemption after purchase		1st		2nd		3rd		4th		5th		6th		7th
Contingent deferred sales charge		4	%	4	%	3	%	3	%	2	%	1	%	0	%

 

Class C Shares.  You may purchase Class C shares at net asset value without an initial sales charge. However, a CDSC of 1% will generally be deducted from your redemption proceeds if you redeem within 12 months of your purchase.

 

Class I Shares.  Eligible investors may purchase Class I shares at net asset value without an initial sales charge or a CDSC upon redemption.

 

Class R1, Class R2, Class R3, Class R4, and Class R6 Shares.  Eligible investors may purchase Class R1, Class R2, Class R3, Class R4, and Class R6 shares at net asset value without an initial sales charge or a CDSC upon redemption.

 

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MFS Corporate Bond Fund

 

Calculation Of CDSC.  As discussed above, certain investments in Class A, Class B, and Class C shares are subject to a CDSC. For purposes of calculating the CDSC, purchases made on any day during a calendar month will age one month at the close of business on the last day of that month, and at the close of business on the last day of each subsequent month.  The CDSC is based on the original purchase cost or the current market value of the shares being sold, whichever is less. For purposes of determining the CDSC, if you sell only some of your shares, shares not subject to a CDSC are sold first, followed by shares held the longest.

 

Shares acquired through reinvestment of distributions are not subject to a CDSC.

 

Distribution and Service Fees

 

The fund has adopted a plan in accordance with Rule 12b-1 under the Investment Company Act of 1940, as amended (the “Distribution Plan”). Under the Distribution Plan, the fund pays distribution and/or service fees to MFD to support the sale and distribution of Class A, Class B, Class C, Class R1, Class R2, and Class R3 shares, and/or shareholder servicing and account maintenance activities. These distribution and/or service fees equal on an annual basis up to the following maximum percentages of average daily net assets of the class:

 

CLASS		MAXIMUM DISTRIBUTION FEE		MAXIMUM SERVICE FEE		MAXIMUM TOTAL DISTRIBUTION AND SERVICE FEE
Class A		0.00	%	0.25	%	0.25	%
Class B		0.75	%	0.25	%	1.00	%
Class C		0.75	%	0.25	%	1.00	%
Class R1		0.75	%	0.25	%	1.00	%
Class R2		0.25	%	0.25	%	0.50	%
Class R3		0.00	%	0.25	%	0.25	%

 

These fees are paid out of fund assets of the applicable class of shares. Because these fees are an ongoing expense of the fund, they increase the cost of your investment over time and may cost you more than other types of sales charges.

 

MFD has voluntarily agreed to rebate to the class a portion of such class’ 0.25% service fee attributable to accounts for which there is no financial intermediary specified on the account except for accounts attributable to seed money of MFS or an affiliate.  The fund has not adopted a Rule 12b-1 plan with respect to its Class I, Class R4, or Class R6 shares.

 

Financial Intermediary Compensation

 

The term “financial intermediary” refers to any broker/dealer, bank (including bank trust departments), registered investment adviser, financial planner, retirement plan administrator, third-party administrator, insurance company, and any other institution having a selling, administration, or any similar agreement with MFD, MFS, or any of their affiliates.

 

Financial intermediaries receive various forms of compensation in connection with the sale of shares of a fund and/or the servicing of shareholder accounts. Financial intermediaries may receive such compensation (i) in the form of up-front commissions and ongoing asset-based compensation paid by MFD based on sales charges received and expected to be received by MFD from shareholders and Distribution Plan distribution and service payments received by MFD from the fund, (ii) in the form of shareholder servicing payments paid by an affiliate of MFD based on the receipt of such payments by MFD or its affiliates from the fund, and (iii) in the form of payments paid by MFD from MFD’s own additional resources.

 

Financial intermediaries may receive up-front commissions of up to the following percentage amounts for sales of the following share classes:

 

SHARE CLASS		UP FRONT COMMISSION AS A PERCENTAGE OF OFFERING PRICE
Class A		4.25	%
Class B		3.75	%
Class C		1.00	%

 

In addition, financial intermediaries may receive payments from MFD from MFD’s own additional resources as incentives to market the MFS funds, to cooperate with MFD’s promotional efforts and/or in recognition of their marketing, administrative services, and/or transaction processing support. This compensation from MFD is not reflected in the fees and expenses listed in the fee table section of the fund’s prospectus.  MFD compensates financial intermediaries based on criteria established by MFD from time to time that consider, among other factors, the distribution potential of the financial intermediary, the types of products and programs offered by the financial intermediary, the level and/or type of marketing and administrative support provided by the financial intermediary, the level of assets attributable to and/or sales by the financial intermediary and the quality of the overall relationship with the financial intermediary.

 

These additional payments by MFD may take the form of payments to financial intermediaries that provide marketing support and administrative services to MFD with respect to fund shares sold or held through the financial intermediary’s distribution network and/or through programs such as retirement programs, qualified tuition programs, fund supermarkets, fee-based advisory or wrap fee programs, bank trust programs, and insurance (e.g., individual or group annuity) programs. MFD may also make payments to financial intermediaries to help offset the cost associated with client account maintenance support, statement preparation, and transaction processing. To the extent permitted by U.S. Securities and Exchange Commission (SEC) and Financial Industry Regulatory Authority (FINRA) rules and other applicable laws and regulations, MFD may make other payments or allow other promotional incentives or payments to financial intermediaries.

 

The types of payments described above are not exclusive and such payments can be significant to the financial intermediary. In addition, the compensation that financial intermediaries receive may vary by class of shares sold and among financial intermediaries. Depending upon the arrangements in place at any particular time, financial intermediaries may have a financial incentive to recommend a particular fund or share class.

 

You can find further details in the SAI about the payments made by MFD and its affiliates and the services provided by financial intermediaries. Financial intermediaries may charge you additional fees and/or commissions other than those disclosed in this prospectus. You can ask your financial intermediary for information about any payments it receives from MFD and its affiliates and any services it provides, as well as about fees and/or commissions it charges. Financial intermediaries that sell fund shares may also act as a broker/dealer in connection with a MFS fund’s purchase or sale of portfolio securities. However, the fund and MFS do not consider financial intermediaries’ sales of shares of an MFS fund as a factor when choosing broker/dealers to effect portfolio transactions for the MFS funds.

 

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MFS Corporate Bond Fund

 

How To Purchase, Redeem, and Exchange Shares

 

You may purchase, redeem, and exchange shares of the fund in the manner described below. The fund is generally only available to U.S. residents with a valid U.S. tax identification number (and to certain other qualified investors). If you buy or sell shares of a fund through a retirement account, Section 529 plan, or financial intermediary, the procedures for buying, selling, and exchanging shares of the fund and the features, policies, and fees may differ from those discussed in this prospectus. Investment minimums may be waived or reduced for certain types of investors and investments and your financial intermediary may have additional minimums.

 

How to Purchase Shares

 

Your shares will be bought at the offering price (the net asset value per share plus any applicable initial sales charge) next calculated after your purchase order is received in proper form. Your financial intermediary is responsible for transmitting your purchase order to the fund in proper form and in a timely manner. MFSC reserves the right to reject any purchase order that is not in proper form. The specific requirements for proper form depend on the type of account and transaction and the method of purchase; contact MFSC if you have questions about your particular circumstances. Certain restrictions apply to the use of a transfer on death registration.  You or your financial intermediary should contact MFSC to obtain a Transfer on Death registration form and for information regarding MFSC’s other requirements for transfer on death registrations. If payment for a purchase order is not received by the time required under applicable law, your purchase order may be cancelled and your financial intermediary could be liable for any costs or losses.

 

The fund may reject for any reason, or cancel as permitted or required by law, any purchase orders. The fund may stop offering shares completely, or may offer shares only on a limited basis, for a period of time or permanently.

 

The fund is required by law to obtain from you certain information that will be used to verify the identity of the account owner. If you do not provide the information, the fund will not be able to open your account. The fund must also take certain steps to verify that the account information you provide is correct.

 

Purchases of Class B shares are closed to new and existing investors except through reinvestment of dividends and capital gain distributions. Existing investors may continue to exchange their Class B shares for the same share class of another MFS fund.

 

Class A, Class B, and Class C Shares.  You can establish an account by having your financial intermediary process your purchase or by contacting MFSC directly.

 

Purchases of Class B shares are subject to a total account value limitation at the time of purchase of $99,999, and purchases of Class C shares are subject to a total account value limitation at the time of purchase of $499,999. If your existing accounts for all share classes held with the MFS funds have a total value equal to $99,999 for Class B share purchases or $499,999 for Class C share purchases, you will not be able to purchase Class B or Class C shares, as applicable. For the purpose of determining your total account value, existing accounts for all share classes held with the MFS funds that are linked under a Letter of Intent or Right of Accumulation will be included.

 

The fund or its agents may at their discretion accept a purchase request for Class B shares or Class C shares that would otherwise exceed the total account value limitation of $99,999 and $499,999, respectively, under certain circumstances, including purchases by certain types of group or sponsored retirement plans.

 

Class I Shares.  You can establish an account through your MFD representative, by having your financial intermediary process your purchase, or by contacting MFSC directly.

 

Class R1, Class R2, Class R3, Class R4, and Class R6 Shares.  You can establish an account through your financial intermediary or by contacting MFSC directly.  For Class R6 investors, you can also establish your account through your MFD representative.

 

Additional Purchases

 

You may purchase additional shares through your financial intermediary or MFSC.

 

Additional Purchases Directly Through MFSC.

 

●                  Mail.  You may purchase additional shares by mailing a check with your investment instructions to MFSC.

 

●                  Telephone.  You may purchase additional shares by phone from your pre-designated bank account. You must elect this privilege on your account application or service application.  Purchases via telephone are not available for certain types of accounts.

 

●                  Internet.  You may purchase additional shares from a pre-designated bank account via the Internet at mfs.com (MFS Access). You must elect this privilege on your account application or service application and establish a password on MFS Access to use this service. Purchases via the Internet are not available for Class R1, Class R2, Class R3, Class R4, and Class R6 shares, and certain types of accounts.

 

●                  Wire.  To purchase additional shares by wire, call MFSC for instructions.

 

●                  Automatic Investment Plan.  You may purchase additional shares by automatically investing a designated amount from your checking or savings account on any day of the month. You must elect this privilege on your account application or service application.

 

Additional Purchases Through Your Financial Intermediary.  You can have your financial intermediary purchase shares on your behalf. Your financial intermediary will be responsible for furnishing all necessary documents to MFSC and may charge you for this service.

 

How to Redeem Shares

 

Your shares will be sold at the net asset value per share next calculated after your redemption order is received in proper form, minus any applicable CDSC and/or other fees.  Your financial intermediary is responsible for transmitting your redemption order to the fund in proper form and in a timely manner. MFSC reserves the right to reject any redemption request that is not in proper form. The specific requirements for proper form depend on the type of account and transaction and the method of redemption; contact MFSC if you have questions about your particular circumstances.

 

In certain circumstances, you will need to have your signature guaranteed and/or submit additional documentation to redeem your shares. In general, no signature guarantee is required for a redemption order for up to $100,000 that is signed by all owners or fiduciaries identified in the account registration, paid as registered, and mailed to the address of record. However, if you have changed your address of record within 30 days of your redemption order, a Medallion signature guarantee will generally be required. A Medallion signature guarantee will also generally be required if you want to send your redemption proceeds to a pre-designated bank account that was added or changed on your account within 30 days of your redemption order.

 

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MFS Corporate Bond Fund

 

The fund typically processes your redemption proceeds, after your request is received in proper form, by the end of the next business day for payment by wire and payment processed through DTCC’s Defined Contribution Clearance & Settlement System or Fund/SERV system (financial intermediaries can choose to have payments processed through the Fund/SERV system by the end of the second business day instead of the next business day), and by the end of the second business day for payment by check and Automated Clearing House.  However, the fund may delay processing your redemption request for up to seven days.  Under unusual circumstances, such as when the NYSE is closed, trading on the NYSE is restricted, or as permitted by the SEC, the fund may suspend redemptions or postpone payment for more than seven days.

 

If you recently purchased shares and subsequently request a redemption, redemption proceeds (other than in an exchange) for the shares you recently purchased will generally be delayed until money from such purchases sufficient to cover your redemption has been received and collected.  Receiving and collecting payment can take up to seven business days after a purchase.  You can avoid this delay by purchasing shares by wire transfer.

 

The fund typically expects to meet redemption requests by holding cash and/or cash equivalents, selling investments, and using overdraft provisions or lines of credit.  The fund may also meet redemption requests by redeeming shares in kind for large redemptions or during stressed market conditions.  If, during any 90-day period, you redeem shares in an amount greater than the lesser of $250,000 or 1% of fund net assets, and if MFS determines it to be feasible and appropriate, the fund may pay the redemption amount above such threshold by a distribution in kind of portfolio securities (redemption in kind).  In the event that the fund makes a redemption in kind, you should expect to incur brokerage and other transaction charges when converting the securities to cash, and the securities will likely increase or decrease in value before you sell them.

 

You may redeem your shares either by having your financial intermediary process your redemption or by contacting MFSC directly.

 

Redeeming Directly Through MFSC.

 

●                  Mail.  To redeem shares by mail, you can send a letter, or the applicable redemption form, to MFSC with the name of the fund, your account number, and the number of shares or dollar amount to be redeemed. MFSC currently charges a fee to send your proceeds via overnight mail.

 

●                  Telephone.  If a signature guarantee is not required, you can call MFSC to have shares redeemed from your account and proceeds mailed to the address of record on the account. MFSC currently charges a fee to send your proceeds via overnight mail. You can also call MFSC to have shares redeemed from your account and the proceeds sent directly to a pre-designated bank account. You must elect this privilege on your account application or service application if you wish to have proceeds sent to your bank account. Telephone redemptions are not available for certain types of accounts.

 

●                  Internet.  If a signature guarantee is not required, you can have shares redeemed from your account via the Internet at mfs.com (MFS Access) and the proceeds mailed to the address of record on the account. You can also have shares redeemed from your account via MFS Access and the proceeds sent directly to a pre-designated bank account. You must elect this privilege on your account application or service application and establish a password on MFS Access to use this service. Redemptions via the Internet are not available for Class R1, Class R2, Class R3, Class R4, and Class R6 shares, and certain types of accounts.

 

●                  Systematic Withdrawal Plan (not available for Class R1, Class R2, Class R3, Class R4, and Class R6 shares).  If you have a balance of at least $5,000 in your account in the fund, you may elect to automatically receive (or designate someone else to receive) regular periodic payments (of at least $50 if by check) through an automatic redemption of such classes. The fund may terminate any Systematic Withdrawal Plan for an account if the value of the account falls below $5,000 as a result of share redemptions (other than as a result of a Systematic Withdrawal Plan).  Please contact MFSC or your financial intermediary for details.

 

●                  Checkwriting.  You may redeem your Class A and Class C shares by writing checks against your account. There is no charge for this service. You must elect this privilege on your account application to use this service. Shares in your account equal in value to the amount of the check plus the applicable CDSC (if any) and any income tax required to be withheld (if any), are redeemed to cover the amount of the check. If your account value is not great enough to cover these amounts, your check will be dishonored. Checkwriting is not available for all accounts.

 

Redeeming Through Your Financial Intermediary.  You can have your financial intermediary process a redemption on your behalf. Your financial intermediary will be responsible for furnishing all necessary documents to MFSC and may charge you for this service.

 

Signature Guarantee/Additional Documentation.  If a Medallion signature guarantee is required, your signature may be guaranteed by an eligible bank, broker/dealer, credit union, national securities exchange, registered securities association, clearing agency, or savings association that participates in a Medallion program recognized by the Securities Transfer Association. MFSC may require additional documentation for certain types of registrations and under certain circumstances. Signature guarantees and this additional documentation shall be accepted in accordance with policies established by MFSC, and MFSC may, at its discretion, change and make certain exceptions to these requirements. Please contact MFSC with any questions and for the requirements for your particular situation.

 

Share Certificates.  If certificates are outstanding for your shares, you may only redeem such shares by mailing the certificates to MFSC. Telephone, electronic, and systematic withdrawal plan redemptions and checkwriting are not available if certificates are outstanding for your shares.

 

Involuntary Redemptions.  Because it is costly to maintain small accounts, the MFS funds have reserved the right to redeem your Class A, Class B, or Class C shares without your permission when your account contains less than $500 for any reason, including market fluctuation. Before the fund makes such a redemption, you will be notified and given 60 days to increase your investment to at least $500. Certain accounts are not subject to these provisions.  Any applicable CDSC will be waived for shares redeemed due to the small size of a shareholder’s account.

 

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MFS Corporate Bond Fund

 

In addition, the MFS funds have reserved the right to redeem your shares without your permission in cases of threatening conduct or suspicious, fraudulent, or illegal activity.  Any applicable CDSC will be assessed upon redemption of your shares.

 

How to Exchange Shares

 

An exchange involves the redemption of shares of one fund and the purchase of shares of another fund.

 

Exchange Privilege.  You can exchange your shares for shares of the same class, if available, of most other MFS funds at their respective net asset values by having your financial intermediary process your exchange request or by contacting MFSC directly.

 

You can exchange your Class A shares and your Class I shares for shares of MFS U.S. Government Money Market Fund, if available, according to the terms of such fund’s prospectus.

 

You can exchange your Class R6 shares of the fund for shares of MFS Institutional International Equity Fund, if available, subject to the eligibility requirements for such shares, according to the terms of MFS Institutional International Equity Fund’s prospectus.

 

Shares otherwise subject to a CDSC will not be charged a CDSC in an exchange. Shares will retain the CDSC schedule in effect based upon a pro rata share of the CDSC from the exchanged fund and the original purchase date of the shares subject to the CDSC.

 

You should read the prospectus of the MFS fund into which you are exchanging and consider the differences in investment objectives, policies, and risks, and in fees and expenses, before making an exchange. The exchange privilege may be changed or discontinued at any time, and all exchanges are subject to certain limitations and the MFS funds’ policies concerning disruptive trading practices, which are designed to protect the funds and their shareholders from the harmful effects of frequent trading. No more than ten exchanges may be made in any one exchange request by telephone.

 

The MFS funds allow certain financial intermediaries to place exchange orders on behalf of a group of their discretionary investment advisory clients (“group exchange orders”). As with any exchange request, the funds and their agents reserve the right to reject any group exchange order, and the funds’ agents will generally reject any group exchange order received by the funds or their agents after 1 p.m., Eastern time. In addition, MFD has agreements with certain financial intermediaries which set forth the terms and conditions under which group exchange orders may be placed by these financial intermediaries. These conditions may be more restrictive than those applicable to individual exchange orders, and may include the requirement to provide the funds or their agents with advance notice of group exchange orders.

 

Automatic Exchange Plan (not available for Class R1, Class R2, Class R3, Class R4, and Class R6 shares).  If you have a balance of at least $2,000 in your account in the fund, you may participate in the automatic exchange plan, a dollar-cost averaging program. This plan permits you to make automatic periodic exchanges from your account in the fund for shares of the same class of other MFS funds. Exchanges will generally be made at net asset value without any sales charges; however, you will pay the initial sales charge, if applicable, if you have not already paid this charge on these shares.

 

Disruptive Trading

 

General Purchase and Exchange Limitation Policy.  The MFS funds reserve the right to restrict, reject, or cancel, without any prior notice, any purchase or exchange order, including transactions believed to represent frequent or other disruptive trading activity. In the event that MFSC rejects or cancels an exchange request, neither the redemption nor the purchase side of the exchange will be processed.  Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC’s judgment, in consultation with MFS, as appropriate, such delay would be in the fund’s best interest, in which case both the redemption and purchase side of the exchange will receive the funds’ net asset values at the conclusion of the delay period.

 

Disruptive Trading Risks.  To the extent that the MFS funds or their agents are unable to curtail disruptive trading practices in a fund (e.g., frequent trading) or to the extent there are large or frequent redemptions in a fund, these purchases and/or redemptions can interfere with the efficient management of the fund’s portfolio, may result in increased transaction and administrative costs, and may adversely impact the fund’s performance.

 

In addition, to the extent that the fund invests in foreign securities, the interests of long-term shareholders may be diluted as a result of time-zone arbitrage, a short-term trading practice that seeks to exploit changes in the value of the fund’s investments that result from events occurring after the close of the foreign markets on which the investments trade, but prior to the time the fund determines its net asset value. The fund’s use of fair valuation can serve to reduce arbitrage opportunities available to short-term traders, but there is no assurance that the fund’s fair valuation policies and procedures will prevent dilution of the fund’s net asset value by short-term traders.

 

To the extent that the fund invests in securities that trade infrequently or are difficult to value, such as the securities of smaller companies, high yield debt instruments, and floating rate loans, the interests of long-term shareholders may be diluted as a result of price arbitrage, a short-term trading strategy that seeks to exploit perceived pricing inefficiencies in the fund’s investments. Such short-term trading strategies may interfere with efficient management of the fund’s portfolio to a greater degree than funds that invest in more frequently traded or liquid securities, in part because the fund may have difficulty selling these portfolio securities at advantageous times or prices to satisfy large and/or frequent redemption requests. Any successful price arbitrage may also cause dilution in the value of fund shares held by other shareholders.

 

Frequent Trading.  The fund is not intended to serve as a vehicle for frequent trading. The Board of Trustees of the fund has adopted the purchase and exchange limitation policy described below, which it believes is reasonably designed to discourage frequent fund share transactions. MFSC seeks to monitor and enforce this policy, subject to oversight by the Board of Trustees. The fund may alter its policies at any time without notice to shareholders.

 

MFSC will generally restrict, reject or cancel purchase and exchange orders into the fund if MFSC determines that an accountholder has made two exchanges, each in an amount of $15,000 or more, out of an account in the fund during a calendar quarter (“two exchange limit”). This policy does not apply to MFS money market funds or to exchanges initiated by a retirement plan trustee or sponsor rather than by a plan participant, and other similar non-discretionary exchanges (e.g., in connection with fund mergers/acquisitions/liquidations).  MFSC may make exceptions to this policy if, in its judgment, the transaction does not represent frequent trading activity, such as purchases made through systematic purchase plans (but not systematic exchange plans), payroll contributions, or distribution investment programs. In applying this policy, MFSC considers the information available to it at the time and reserves the right to consider trading effected through multiple accounts that are under common ownership, control, or influence to be trading out of a single account.

 

Exchanges made on the same day in the same account are aggregated for purposes of counting the number and dollar amount of exchanges made by the accountholder (e.g., an accountholder

 

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MFS Corporate Bond Fund

 

who on the same day exchanges $16,000 from the fund into two other MFS funds, by exchanging $8,000 into each of the two MFS funds, will be viewed as having made one exchange transaction exceeding $15,000 in value).

 

Omnibus accounts, in which shares are held in the name of a financial intermediary on behalf of multiple underlying shareholders, are a common form of holding shares among certain financial intermediaries such as brokers, retirement and Section 529 plans, investment advisers, and insurance companies.

 

Financial intermediaries are required to reject any purchase or exchange orders in the fund if they believe the orders represent frequent trading activity unless they notify MFSC or an affiliate in writing that they do not monitor for frequent trading (“Waived Financial Intermediary”). With respect to Waived Financial Intermediaries, MFSC will take action reasonably designed to discourage frequent trading that is not in the best interests of the fund by the customers of such Waived Financial Intermediary, including requesting underlying shareholder account data more frequently than from other financial intermediaries.

 

With respect to omnibus accounts that provide MFSC with underlying shareholder data daily, MFSC will apply the two exchange limit directly to underlying shareholders.  For all other accounts which MFSC determines are omnibus accounts, MFSC will apply the two exchange limit to the omnibus account itself.  Applying the two exchange limit to the omnibus account itself will not necessarily detect violations of the two exchange limit by underlying shareholders. If the financial intermediary associated with an omnibus account that has triggered the two exchange limit demonstrates to MFSC, as determined in MFSC’s sole discretion, that no single underlying shareholder triggered the two exchange limit, then MFSC will remove any restrictions, rejections or cancellations imposed on the account.  If the financial intermediary demonstrates to MFSC that a single underlying shareholder triggered the two exchange limit and that the financial intermediary itself will apply applicable restrictions, rejections or cancellations to that underlying shareholder, MFSC will likewise remove any restrictions, rejections or cancellations imposed on the omnibus account.  Otherwise, MFSC will continue to apply the two exchange limit to the omnibus account.

 

Certain financial intermediaries may use procedures to restrict frequent trading by their customers who invest in the fund while others may not employ any procedures to restrict frequent trading.  Such procedures, if any, may be less restrictive than the fund’s purchase and exchange limitation policy, may permit transactions not permitted by the fund’s purchase and exchange limitation policy, including transactions in excess of the two exchange limit, and/or may prohibit transactions not subject to the fund’s purchase and exchange limitation policy.  You should consult your financial intermediary about any restrictions it imposes on frequent trading.

 

There is no assurance that MFSC will be able to detect or prevent frequent trading.  Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and MFSC is generally not able to identify trading by a particular underlying shareholder within an omnibus account, which makes it difficult or impossible to determine if a particular underlying shareholder is engaged in frequent trading.

 

MFSC reviews trading activity to detect trading activity that may be indicative of frequent trading based on its internal parameters for detecting frequent trading, including reviewing transactions (including exchanges) that exceed a certain dollar amount, transactions involving similar dollar amounts, or transactions that occur close in time to other transactions in the same account or in multiple accounts that are under common ownership or influence.  Any or all of these parameters (including those not listed) may change at any time.  If MFSC detects suspicious trading activity at the omnibus account level, it will contact the financial intermediary to request underlying shareholder level activity to determine whether there is underlying shareholder level frequent trading.  However, the underlying shareholder data received may not reflect information about the ultimate underlying shareholders because there may be multiple layers of omnibus accounts. If frequent trading is identified, MFSC will take appropriate action, such as requesting the financial intermediary to prohibit purchases into the account by the underlying shareholder, requiring purchases by the underlying shareholder to be submitted only by mail, or prohibiting purchases from the financial intermediary.

 

MFSC’s ability to monitor and deter frequent trading in omnibus accounts depends on, among other factors, the frequency with which MFSC requests underlying shareholder account data from omnibus accounts.  MFSC expects to request underlying shareholder data based on its assessment of the likelihood of frequent trading by underlying shareholders among other factors.  MFSC expects to request underlying shareholder data from Waived Financial Intermediaries more frequently than from other financial intermediaries.  There is no assurance that MFSC will request data with sufficient frequency to detect or prevent frequent trading in omnibus accounts effectively.

 

Other Considerations

 

Unauthorized Transactions.  MFS will not be responsible for losses that result from unauthorized transactions unless MFSC does not follow procedures reasonably designed to verify your identity. If an account has more than one owner or authorized person, MFSC will accept telephone and online instructions from any one owner or authorized person, except MFSC will require instructions for a redemption from all trustees of trust accounts registered with multiple trustees. It is important that you contact MFSC immediately about any transactions made through MFSC you believe to be unauthorized.

 

Ability to Contact MFSC.  Certain methods of contacting MFSC, such as by mail, telephone, or electronically, may be unavailable or delayed (for example, after natural disasters, during periods of significant/major political, social, or economic instability, or in the event of a cyber security incident).

 

Unclaimed Accounts and Uncashed Checks.  If your account has no activity for a certain period of time and/or mail sent to you on behalf of the fund is returned by the post office, the fund may be required to transfer your account and any assets related to uncashed checks to the appropriate state under the state’s abandoned property laws. To avoid such action, it is important to keep your account address up to date and periodically communicate with the fund, MFSC, or your financial intermediary. When a traditional IRA account is transferred to a state as abandoned property, the Internal Revenue Service considers the transfer a taxable distribution subject to federal income tax withholding and reporting.  The fund and MFSC will not be liable to shareholders or their representatives for good faith compliance with abandoned property laws.

 

Reservation of Other Rights.  In addition to the rights expressly stated elsewhere in this prospectus, subject to applicable rules, laws, and regulations, MFSC reserves the right to: 1) alter, add, or discontinue any conditions of purchase, redemption, service, or privilege at any time without notice; 2) freeze any account or suspend account services when MFSC has received reasonable notice (written or otherwise) of a dispute between registered or beneficial account owners or when MFSC believes a fraudulent transaction may occur or has occurred; and 3) change, impose, discontinue, or waive any fee it charges.

 

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MFS Corporate Bond Fund

 

Anti-Money Laundering Restrictions.  Federal law requires the fund to implement policies and procedures reasonably designed to prevent, detect and report money laundering and other illegal activity. The fund, consistent with applicable federal law, may redeem your shares and close your account; suspend, restrict or cancel purchase and redemption orders; process redemption requests and withhold your proceeds; and take other action if it is unable to verify your identity within a reasonable time or conduct required due diligence on your account or as otherwise permitted by its anti-money laundering policies and procedures. Any applicable CDSC will be assessed upon redemption of your shares.

 

Confirmations in Quarterly Statements.  Transactions made under certain periodic investment and withdrawal programs (including reinvestment plans) will be confirmed on quarterly account statements.

 

Other Information

 

Valuation

 

The price of each class of the fund’s shares is based on its net asset value. The net asset value of each class of shares is determined each day the NYSE is open for trading as of the close of regular trading on the NYSE (generally 4:00 p.m. Eastern time). However, net asset value may be calculated earlier in emergency situations or as otherwise permitted by the SEC. Net asset value per share is computed by dividing the net assets allocated to each share class by the number of shares outstanding for that class. On days when the NYSE is closed (such as weekends and holidays), net asset value is not calculated, and the fund does not transact purchase and redemption orders. To the extent the fund’s assets are traded in other markets on days when the fund does not price its shares, the value of the fund’s assets will likely change when you will not be able to purchase or redeem shares of the fund.

 

To determine net asset value, the fund’s investments for which reliable market quotations are readily available are valued at market value, and funds in which the fund invests are generally valued at their net asset value per share. Certain short term debt instruments may be valued at amortized cost.

 

The Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund’s investments (including any fair valuation) to MFS pursuant to valuation policies and procedures approved by the Board of Trustees. If MFS determines that reliable market quotations are not readily available, investments are valued at fair value as determined in good faith by MFS in accordance with such procedures under the oversight of the Board of Trustees.

 

Under the fund’s valuation policies and procedures, market quotations are not considered to be readily available for most types of debt instruments and many types of derivatives. These investments are generally valued at fair value based on information from third-party pricing services. These valuations can be based on both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data.

 

In addition, investments may be valued at fair value if MFS determines that an investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as a foreign exchange or market) and prior to the determination of the fund’s net asset value, or after the halting of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. MFS generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment.

 

The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.

 

Distributions

 

The fund intends to declare a dividend daily and to pay any dividends to shareholders at least monthly.

 

Any capital gains are distributed at least annually.

 

Distribution Options

 

The following distribution options are generally available for Class A, Class B, Class C, and Class I shares:

 

●                  Dividend and capital gain distributions automatically reinvested in additional shares (this option will be assigned if no other option is specified);

 

●                  Dividend distributions in cash; capital gain distributions automatically reinvested in additional shares;

 

●                  Dividend and capital gain distributions in cash; or

 

●                  Dividend and capital gain distributions automatically reinvested into the same class of shares of another MFS fund (not available for Class B shares).

 

Not all options are available for every class or every account.

 

Dividends and capital gain distributions for Class R1, Class R2, Class R3, Class R4, and Class R6 shares can only be reinvested in additional shares of the fund, except with respect to Class R6 shares, certain institutional shareholders, shareholders who purchase shares through brokerage programs of certain financial intermediaries, and shareholders who purchase shares through asset-based fee programs of certain financial intermediaries may elect any of the other distribution options described above.

 

The distribution option for accounts with dividend distributions of less than $10 generally will be changed to reinvestment in additional shares of the fund. If you have elected to receive distributions in cash, and the postal service is unable to deliver checks to your address of record, or you do not respond to mailings from MFSC with regard to uncashed distribution checks, your distribution option may be converted to having all distributions reinvested in additional shares. You should contact MFSC to change your distribution option, and your request to do so must be received by MFSC before the record date for a distribution in order to be effective for that distribution. No interest will accrue on amounts represented by uncashed distribution checks.

 

Tax Considerations

 

The following discussion is very general. You are urged to consult your tax adviser regarding the effect that an investment in the fund will have on your particular tax situation, including possible foreign, state, and local taxes. This discussion does not apply to shares of the fund held through tax-advantaged retirement plans or by shareholders that are not “U.S. persons” under the Internal Revenue Code of 1986, as amended.

 

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MFS Corporate Bond Fund

 

The fund expects to distribute substantially all of its income and gains annually. Distributions from the fund are taxable whether you receive them in cash or reinvest them in additional shares. If you buy shares when the fund has realized but not yet distributed ordinary income or capital gains, you will pay full price for the shares and then receive a portion back as a taxable distribution.

 

Any gain resulting from the redemption, sale, or exchange of your shares will generally also be subject to tax.

 

For federal income tax purposes, distributions of investment income are generally taxable as ordinary income. Taxes on distributions of capital gains are determined by how long the fund owned or is deemed to have owned the investments that generated them, rather than how long you have owned your shares. Distributions of gains from the sale of investments that the fund owned for more than one year and that are properly reported by the fund as capital gain dividends will be treated as long-term capital gains includible in net capital gain and taxed to individuals at reduced rates. Distributions of gains from the sale of investments that the fund owned for one year or less will be taxable as ordinary income. If some or all of the fund’s income derives from “qualified dividend income” and if you are an individual who meets holding period and other requirements with respect to the fund’s shares, those distributions that are properly reported by the fund as derived from qualified dividend income are taxed to you at the reduced rates applicable to net capital gains. The fund does not expect a significant portion of fund distributions to be derived from qualified dividend income.

 

The fund’s investments in certain debt instruments may cause the fund to recognize income in excess of the cash generated by such instruments. Thus, the fund could be required at times to liquidate other investments in order to satisfy its distribution requirements.

 

A 3.8% Medicare contribution tax is generally imposed on distributions paid by the fund (other than exempt-interest dividends, if any) to, and net gains recognized on the sale, redemption, exchange, or other taxable disposition of shares of the fund by certain individuals, estates and trusts to the extent their income exceeds certain threshold amounts.

 

The fund’s investments in foreign securities may be subject to foreign withholding or other taxes, which will decrease the fund’s return on those securities; you generally are not expected to be eligible to claim a credit (or a deduction) for such amounts on your federal income tax return.

 

The Form 1099 that is provided to you early each year details your distributions from the fund and how they are treated for federal tax purposes, and cost basis information for shares purchased on or after January 1, 2012, that you redeemed, sold, or exchanged. Our default method for calculating cost basis is average cost basis. More information about other cost basis methods and a cost basis selection/change form are available on mfs.com. If your account is held by your financial intermediary, you must contact your financial intermediary to obtain information about available cost basis methods and cost basis elections for your account.

 

Information about the Summary Prospectus, Prospectus, and SAI

 

The summary prospectus, prospectus, and SAI for a fund provide information concerning the fund.  The summary prospectus, prospectus, and SAI are updated at least annually and any information provided in a summary prospectus, prospectus, or SAI can be changed without a shareholder vote unless specifically stated otherwise.  The summary prospectus, prospectus, and SAI are not contracts between the fund and its shareholders and do not give rise to any contractual rights or obligations or any shareholder rights other than any rights conferred explicitly by federal or state securities laws that may not be waived.

 

Provision of Financial Reports and Summary Prospectuses

 

The fund produces financial reports every six months and updates its summary prospectus and prospectus annually. To avoid sending duplicate copies of materials to households, only one paper copy of the fund’s annual and semiannual report and summary prospectus may be mailed to shareholders having the same last name and residential address on the fund’s records. However, any shareholder may contact MFSC (please see back cover for address and telephone number) to request that copies of these reports and summary prospectuses be sent personally to that shareholder.

 

Additional Information on Fees and Expenses and Performance

 

Fees and Expenses

 

The annual fund operating expenses shown in “Fees and Expenses” are based on annualized expenses reported during the fund’s most recently completed fiscal year expressed as a percentage of a class’ average net assets during the period.  Annual fund operating expenses have not been adjusted to reflect the fund’s current asset size. In general, annual fund operating expenses, expressed as a percentage of a class’ average net assets, increase as the fund’s assets decrease. Annual fund operating expenses will likely vary from year to year.

 

Performance Information

 

All performance information shown in the “Class A Bar Chart” and the “Performance Table” reflects any applicable fee reductions and waivers and expense reimbursements in effect during the periods shown; without these, the performance would have been lower.

 

From time to time, the fund may receive proceeds from litigation settlements, without which performance would be lower.

 

The fund commenced operations on May 8, 1974, with the offering of Class A shares, and subsequently offered Class B shares on September 7, 1993, Class C shares on January 3, 1994, Class I shares on January 2, 1997, Class R2 shares on October 31, 2003, Class R1, R3, and R4 shares on April 1, 2005, and Class R6 shares on June 1, 2012.

 

In the “Performance Table,” performance for Class R6 shares includes the performance of the fund’s Class I shares, adjusted to take into account differences in sales loads and class specific operating expenses (such as Rule 12b-1 fees), if any, for periods prior to their offering.

 

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MFS Corporate Bond Fund

 

Financial Highlights

 

The financial highlights are intended to help you understand a fund’s financial performance for the past five years. Certain information reflects financial results for a single fund share. The total returns in the financial highlights represent the rate by which an investor would have earned (or lost) on an investment in a fund (assuming reinvestment of all distributions) held for the entire period. This information has been audited by the fund’s independent registered public accounting firm, whose report, together with the fund’s financial statements, is included in the fund’s Annual Report to shareholders. The fund’s Annual Report is available upon request by contacting MFSC (please see back cover for address and telephone number). The fund’s independent registered public accounting firm is Deloitte & Touche LLP.

 

Class A

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.93		$	13.52		$	13.92		$	13.99		$	14.11
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.42		$	0.43		$	0.41		$	0.42	(c)	$	0.44
Net realized and unrealized gain (loss)		0.96			0.41			(0.39		)	(0.04		)	(0.06		)
Total from investment operations		$	1.38		$	0.84		$	0.02		$	0.38		$	0.38
Less distributions declared to shareholders
From net investment income		$	(0.43	)	$	(0.43	)	$	(0.42	)	$	(0.45	)	$	(0.46	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.43	)	$	(0.43	)	$	(0.42	)	$	(0.45	)	$	(0.50	)
Net asset value, end of period (x)		$	14.88		$	13.93		$	13.52		$	13.92		$	13.99
Total return (%) (r)(s)(t)(x)		10.00			6.39			0.08			2.73		(c)	2.83
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.79			0.79			0.80			0.81		(c)	0.83
Expenses after expense reductions (f)		0.77			0.78			0.79			0.80		(c)	0.82
Net investment income (loss)		2.91			3.16			2.95			3.04		(c)	3.24
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	1,996,170		$	1,654,534		$	1,648,508		$	1,597,201		$	1,709,595

 

Class B

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.90		$	13.50		$	13.89		$	13.96		$	14.08
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.32		$	0.32		$	0.31		$	0.32	(c)	$	0.34
Net realized and unrealized gain (loss)		0.95			0.41			(0.39		)	(0.05		)	(0.06		)
Total from investment operations		$	1.27		$	0.73		$	(0.08	)	$	0.27		$	0.28
Less distributions declared to shareholders
From net investment income		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.36	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.40	)
Net asset value, end of period (x)		$	14.85		$	13.90		$	13.50		$	13.89		$	13.96
Total return (%) (r)(s)(t)(x)		9.20			5.53			(0.60		)	1.96		(c)	2.06
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.54			1.54			1.55			1.56		(c)	1.58
Expenses after expense reductions (f)		1.53			1.53			1.54			1.55		(c)	1.57
Net investment income (loss)		2.18			2.41			2.20			2.30		(c)	2.50
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	21,384		$	33,983		$	47,698		$	61,123		$	72,298

 

18

---

 

MFS Corporate Bond Fund

 

Class C

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.89		$	13.48		$	13.88		$	13.94		$	14.06
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.31		$	0.32		$	0.31		$	0.32	(c)	$	0.34
Net realized and unrealized gain (loss)		0.96			0.42			(0.40		)	(0.04		)	(0.06		)
Total from investment operations		$	1.27		$	0.74		$	(0.09	)	$	0.28		$	0.28
Less distributions declared to shareholders
From net investment income		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.36	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.40	)
Net asset value, end of period (x)		$	14.84		$	13.89		$	13.48		$	13.88		$	13.94
Total return (%) (r)(s)(t)(x)		9.21			5.61			(0.67		)	2.04		(c)	2.06
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.54			1.54			1.55			1.56		(c)	1.58
Expenses after expense reductions (f)		1.53			1.53			1.54			1.56		(c)	1.57
Net investment income (loss)		2.16			2.41			2.20			2.30		(c)	2.50
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	143,988		$	143,872		$	182,315		$	242,889		$	264,424

 

Class I

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.92		$	13.51		$	13.91		$	13.98		$	14.11
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.46		$	0.46		$	0.45		$	0.45	(c)	$	0.47
Net realized and unrealized gain (loss)		0.96			0.42			(0.40		)	(0.04		)	(0.06		)
Total from investment operations		$	1.42		$	0.88		$	0.05		$	0.41		$	0.41
Less distributions declared to shareholders
From net investment income		$	(0.47	)	$	(0.47	)	$	(0.45	)	$	(0.48	)	$	(0.50	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.47	)	$	(0.47	)	$	(0.45	)	$	(0.48	)	$	(0.54	)
Net asset value, end of period (x)		$	14.87		$	13.92		$	13.51		$	13.91		$	13.98
Total return (%) (r)(s)(t)(x)		10.28			6.66			0.33			2.99		(c)	3.01
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.53			0.54			0.55			0.56		(c)	0.57
Expenses after expense reductions (f)		0.52			0.53			0.54			0.56		(c)	0.57
Net investment income (loss)		3.15			3.40			3.19			3.25		(c)	3.48
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	1,306,407		$	1,021,313		$	1,781,450		$	2,005,193		$	720,809

 

19

 

MFS Corporate Bond Fund

 

Class R1

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.90		$	13.49		$	13.89		$	13.95		$	14.07
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.31		$	0.32		$	0.31		$	0.32	(c)	$	0.34
Net realized and unrealized gain (loss)		0.96			0.42			(0.40		)	(0.04		)	(0.06		)
Total from investment operations		$	1.27		$	0.74		$	(0.09	)	$	0.28		$	0.28
Less distributions declared to shareholders
From net investment income		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.36	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.32	)	$	(0.33	)	$	(0.31	)	$	(0.34	)	$	(0.40	)
Net asset value, end of period (x)		$	14.85		$	13.90		$	13.49		$	13.89		$	13.95
Total return (%) (r)(s)(t)(x)		9.20			5.60			(0.67		)	2.04		(c)	2.06
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.54			1.54			1.55			1.56		(c)	1.58
Expenses after expense reductions (f)		1.53			1.53			1.54			1.56		(c)	1.57
Net investment income (loss)		2.16			2.41			2.20			2.30		(c)	2.50
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	5,970		$	6,187		$	6,101		$	6,780		$	7,145

 

Class R2

 

		Year ended
		4/30/20			4/30/19			4/30/18			4/30/17			4/30/16
Net asset value, beginning of period		$	13.93		$	13.53		$	13.92		$	13.99		$	14.11
Income (loss) from investment operations
Net investment income (loss) (d)		$	0.39		$	0.39		$	0.38		$	0.39	(c)	$	0.41
Net realized and unrealized gain (loss)		0.95			0.41			(0.39		)	(0.05		)	(0.06		)
Total from investment operations		$	1.34		$	0.80		$	(0.01	)	$	0.34		$	0.35
Less distributions declared to shareholders
From net investment income		$	(0.39	)	$	(0.40	)	$	(0.38	)	$	(0.41	)	$	(0.43	)
From net realized gain		—			—			—			—			(0.04		)
Total distributions declared to shareholders		$	(0.39	)	$	(0.40	)	$	(0.38	)	$	(0.41	)	$	(0.47	)
Net asset value, end of period (x)		$	14.88		$	13.93		$	13.53		$	13.92		$	13.99
Total return (%) (r)(s)(t)(x)		9.73			6.05			(0.09		)	2.47		(c)	2.58
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.04			1.04			1.05			1.06		(c)	1.08
Expenses after expense reductions (f)		1.03			1.03			1.04			1.05		(c)	1.07
Net investment income (loss)		2.67			2.91			2.70			2.79		(c)	3.00
Portfolio turnover		36			38			38			28			30
Net assets at end of period (000 omitted)		$	31,346		$	38,593		$	43,827		$	49,948		$	58,938

 

20