Exhibit 4.3(a)

AGL RESOURCES INC.

RETIREMENT SAVINGS PLUS PLAN

As amended and restated effective June 28, 2013

AGL RESOURCES INC.

RETIREMENT SAVINGS PLUS PLAN

AGL Resources Inc., a corporation duly organized and existing under the laws of the State of Georgia (the “Controlling Company”), hereby amends and restates the AGL RESOURCES INC. RETIREMENT SAVINGS PLUS PLAN (the “Plan”), effective as of June 28, 2013.

STATEMENT OF PURPOSE

A.    The Plan initially was adopted effective as of January 1, 1986, and was amended and restated on December 22, 1994, then again on February 25, 2002, and January 1, 2005, and was subsequently amended further. The Plan, as set forth in this document, is intended and should be construed as a restatement and continuation of the Plan as previously in effect.

B.    The primary purpose of the Plan is to recognize the contributions made to the Controlling Company and its participating affiliates by employees and to reward those contributions by providing eligible employees with an opportunity to accumulate savings for their future security.

C.    The Controlling Company intends that the Plan be a profit sharing plan and a stock bonus plan, qualified under Sections 401(a) and 401(k) of the Internal Revenue Code of 1986, as amended.

D.     Merged Plans .

1.    Effective as of October 1, 2000, the Controlling Company acquired the stock of Virginia Natural Gas, Inc. (“VNG”) from Consolidated Natural Gas, Inc. Upon the acquisition of VNG, the Virginia Natural Gas, Inc. Hourly Savings Plan and the Virginia Natural Gas, Inc. Employee Savings Plan were merged into the Plan, effective as of October 1, 2000. In addition, because certain VNG employees and former employees had participated in the System Thrift Plan of Consolidated Natural Gas Company and Its Participating Subsidiaries for Employees Who Are Not Represented by a Recognized Union, the Plan accepted a transfer of assets and liabilities from that plan.

2.    The Controlling Company entered into an Agreement and Plan of Merger with Cougar Corporation and NUI Corporation (“NUI”), dated as of July 14, 2004, pursuant to which NUI and its subsidiaries became subsidiaries of the Controlling Company. Effective as of December 1, 2004, the employees of NUI and its subsidiaries, who were active participants in the NUI Corporation Savings and Investment Plan or the NUI Corporation Savings and Investment Plan for Collective Bargaining Employees on November 29, 2004, became Participants in the Plan. For employees who were employed by NUI or its affiliates on November 30, 2004, and who became participants in the Plan, past service credit was granted for eligibility and vesting purposes under the

Plan, and prior to January 1, 2006, the Plan provided separate matching contribution and vesting provisions for such employees.

3.    The Controlling Company acquired additional ownership of SouthStar Energy Services, L.L.C. (“SouthStar”) effective January 1, 2010, causing SouthStar to become an Affiliate. Effective January 1, 2012, SouthStar became a participating employer in the plan, and the SouthStar Energy Services, L.L.C. 401(k) Profit Sharing Plan merged with and into the Plan effective in March of 2012.

4.    Effective December 9, 2011, the Controlling Company acquired Nicor, Inc. and its subsidiaries. Effective as of the date of this restatement, the Nicor Companies Savings Investment Plan has been merged with and into the Plan, and certain nonunion employees of the legacy Nicor companies have become participants in the Plan.

STATEMENT OF AGREEMENT

To amend and restate the Plan with the purposes and goals as described above, the Controlling Company hereby sets forth the terms and provisions as follows:

Table of Contents

ARTICLE 1

DEFINITIONS

For purposes of the Plan, the following terms, when used with an initial capital letter, will have the meanings set forth below unless a different meaning plainly is required by the context.

1.1      Account means, with respect to a Participant or beneficiary, the amount of money or other property in the Trust Fund, as evidenced by the last balance posted in accordance with the terms of the Plan to the account record established for such Participant or beneficiary. The Administrative Committee, as required by the terms of the Plan and otherwise as it deems necessary or desirable in its sole discretion, may establish and maintain separate subaccounts for each Participant and beneficiary. “Account” refers to the aggregate of all separate subaccounts or to individual, separate subaccounts, as may be appropriate in context.

1.2      ACP or Actual Contribution Percentage means the percentage described in Section 6.3(b).

1.3      ACP Tests means the nondiscrimination tests described in Section 6.3.

1.4      Active Participant means, for any Plan Year (or any portion thereof), any Covered Employee who, pursuant to the terms of Article II, has been admitted to, and not removed from, active participation in the Plan since the last date his employment commenced or recommenced; provided, to the extent applicable, “Active Participant” will apply separately to each type of Contribution which has a different eligibility requirement under Section 2.1.

1.5      Administrative Committee means the committee which will act to administer the Plan as provided in Article XII. The Administrative Committee will be the plan administrator, as that term is defined in Code Section 414(g), and the administrator, as that term is defined in ERISA Section 3(16)(A). To the extent that an Administrative Committee is not appointed, the Controlling Company may act in lieu of the Administrative Committee.

1.6      ADP or Actual Deferral Percentage means the percentage described in Section 6.2(b).

1.7      ADP Tests means the nondiscrimination tests described in Section 6.2.

1.8      Affiliate means, as of any date, (i) a Participating Company, and (ii) any company, person or organization which, on such date, (A) is a member of the same controlled group of corporations (within the meaning of Code Section 414(b)) as is a Participating Company; (B) is a trade or business (whether or not incorporated) which controls, is controlled by or is under common control (within the meaning of Code Section 414(c)) with a Participating Company, (C) is a member of an affiliated service group (as defined in Code Section 414(m)) which includes a Participating Company; or (D) is required to be aggregated with a Participating Company pursuant to regulations under Code Section 414(o). Solely for purposes of Sections 6.4, 1.24(a)(3) and 1.24(c), the term “Affiliate” as defined in this Section will be deemed to

include any entity that would be an Affiliate if the phrase “more than 50 percent” were substituted for the phrase “at least 80 percent” in each place the latter phrase appears in Code Section 1563(a)(1).

1.9      After-Tax Account means the separate subaccount established and maintained on behalf of a Participant or beneficiary to reflect his interest in the Trust Fund attributable to traditional After-Tax Contributions.

1.10      After-Tax Contributions means the amounts paid by a Participating Company to the Trust Fund at the election of Participants pursuant to the terms of Section 3.1(c).

1.11      After-Tax Deferral Election means an election by an Active Participant directing the Participating Company of which he is an Employee to withhold a percentage of his current Compensation from his paychecks and to contribute such withheld amount to the Plan as an After-Tax Contribution, pursuant to the terms of Section 3.1(c).

1.12      Annual Additions means the sum of the amounts described in Code Section 415(c)(2).

1.13      Before-Tax Account means the separate subaccount established and maintained on behalf of a Participant or beneficiary to reflect his interest in the Trust Fund attributable to Before-Tax Contributions.

1.14      Before-Tax Contributions means the amounts paid by each Participating Company to the Trust Fund at the election of Participants pursuant to the terms of Section 3.1(a).

1.15      Before-Tax Deferral Election means an election by an Active Participant directing the Participating Companies to withhold a percentage of his current Compensation from his paychecks and to contribute such withheld amount to the Plan as a Before-Tax Contribution pursuant to the terms of Section 3.1(a).

1.16      Beneficiary means the person(s) designated in accordance with Section 11.6 to receive any death benefits that may be payable under the Plan upon the death of a Participant.

1.17      Birdsall Plan means the Birdsall, Inc. Retirement Savings Plan, or successor to such plan, as maintained by an Affiliate.

1.18      Board means the board of directors of the Controlling Company. To the extent any committee of the Board has the authority to act on behalf of the Board, an action taken by such committee will be treated as an action by the Board. A reference to the board of directors of any other Participating Company will specify it as such.

1.19      Break in Service .

(a)      AGL Participants . With respect to a Participant who is not a Nicor Participant, a “Break in Service” means any year during which such Employee fails to complete more than 500 Hours of Service; provided, a Break in Service will not be deemed to have

occurred during any period for which he is granted a Leave of Absence if he returns to the service of an Affiliate within the time permitted, subject to the following:

(1)      A Break in Service will be deemed to have commenced on the first day of the year in which it occurs.

(2)      For purposes of determining whether or not an Employee has incurred a Break in Service, and solely for the purpose of avoiding a Break in Service, an Employee absent from work due to a Maternity or Paternity Leave will be credited with (i) the number of Hours of Service with which he normally would have been credited but for the Maternity or Paternity Leave, or (ii) if the Administrative Committee is unable to determine the hours described in clause (i) hereof, 8 Hours of Service for each day of absence included in the Maternity or Paternity Leave; provided, the maximum number of Hours of Service credited for purposes of this subsection will not exceed 501 hours. Hours of Service so credited will be applied only to the year in which the Maternity or Paternity Leave begins, unless such Hours of Service are not required to prevent the Employee from incurring a Break in Service, in which event such Hours of Service will be credited to the Employee in the immediately following year. No Hour of Service will be credited due to Maternity or Paternity Leave as described in this subsection unless the Employee furnishes proof satisfactory to the Administrative Committee (A) that his absence from work was due to a Maternity or Paternity Leave and (B) of the number of days he was absent due to the Maternity or Paternity Leave. The Administrative Committee will prescribe uniform and nondiscriminatory procedures by which to make the above determinations.

(3)      As used in this subsection, the term “year” means the same 12-month period as forms the basis for determining a Year of Vesting Service.

(b)      Nicor Participants . With respect to a Nicor Participant, a “Break in Service” means, generally, a period of 12 consecutive months beginning on a Severance Date or anniversary of such date, during which an Employee does not complete an Hour of Service. For purposes of determining whether or not the Employee has incurred a Break in Service, and solely for the purpose of avoiding a Break in Service, an Employee absent from work due to a Maternity or Paternity Leave will not have a Break in Service until the second anniversary of the first day of such absence from employment; provided, the period between the first and second anniversary of such first day of absence is not a period of service for any other purpose. For purposes of determining whether or not an Employee has incurred a Break in Service, and solely for the purpose of avoiding a Break in Service, to the extent required under the Family and Medical Leave Act of 1993 and the regulations thereunder, an Employee will be deemed to be performing services for an Affiliate during any period the Employee is granted leave under such Act.

1.20      Catch-Up Contributions means the additional Before-Tax and Roth Contributions that may be made pursuant to the terms of Section 3.1(d) by Participants who have reached age 50 by the last day of a Plan Year.

1.21      Code means the Internal Revenue Code of 1986, as amended, and any succeeding federal tax provisions.

1.22      Company Stock means the common stock of the Controlling Company.

1.23      Company Stock Fund means the Investment Fund that is primarily invested in Company Stock.

1.24      Compensation has the meaning set forth in subsection (a), (b), (c), (d), (e) or (f), whichever is applicable; provided, the annual compensation taken into account under the Plan for a Plan Year (or other applicable period) will not exceed the compensation limit under Code Section 401(a)(17) (as adjusted by the Secretary of the Treasury for cost of living increases). For clarity, a Participant’s Before-Tax Contributions, Roth Contributions and After-Tax Contributions will be determined as a percentage of Compensation without excluding the amounts in excess of the limitation under Code Section 401(a)(17).

(a)      AGL Benefit Compensation . Except as provided in subsection (b), for purposes of determining the amount of Before-Tax, Roth and After-Tax Contributions pursuant to Section 3.1, determining the amount of Matching Contributions pursuant to Section 3.2(a), allocating Supplemental Contributions pursuant to Section 5.4 and for all other purposes except those set forth in subsections (b), (c), (d), (e) and (f) hereof, “Compensation” means the total of the amounts described in subsections (a)(1) and (a)(2) payable by the Affiliates, excluding the amounts described in subsection(a)(3), as follows:

(1)      Such Participant’s base salary (not including premiums); plus

(2)      Such Participant’s overtime, commissions and annual bonuses payable under the terms of the AGL Resources Inc. Annual Incentive Plan (or its successor plan) or any other annual bonus plan sponsored by an Affiliate, as well as any other cash bonus paid by an Affiliate on a regular, periodic basis, such as a quarterly, monthly or semi-annual bonus (but, for clarity, not including retention bonuses, even if they are paid on a periodic basis); excluding

(3)      All amounts otherwise includible that are paid after the Employee’s severance from employment with all Affiliates, except to the extent that (A) the Compensation is paid by the later of 2½ months after severance from employment or the end of the Plan Year that includes the date of severance from employment, and (B)(i) the Compensation is regular compensation for services during the Employee’s regular working hours, or compensation for services outside the Employee’s regular working hours (such as overtime or shift differential), commissions, bonuses or other similar payments, and the Compensation would have been paid to the Employee prior to severance from employment if the Employee had continued in employment with an Affiliate; or (ii) the Compensation is payment for unused accrued bona fide vacation leave that the Employee would have been able to use if employment had continued and the Compensation would have been included in Compensation under the Plan if paid prior to severance from employment. The exclusion under this subsection does not apply to payments to an individual who does not currently perform services for an Affiliate

because of Qualified Military Service, to the extent the payments do not exceed the amounts the individual would have received if the individual had continued to perform services for an Affiliate rather than entering Qualified Military Service. The exclusion in this subsection does not apply to payments to an Employee who is permanently and totally disabled as defined in Code Section 22(e)(3), during the period when the Employee is receiving short-term disability payments. For purposes of this subsection, an Employee will not be considered to have a severance from employment if, in connection with a change of employment, the Employee’s new employer maintains the Plan with respect to the Employee.

(b)      Nicor Participants’ Benefit Compensation . For purposes of determining the amount of Before-Tax, Roth and After-Tax Contributions in Section 3.1 for Nicor Participants, the amount of Matching Contributions in Section 3.2(b) for Nicor Participants, and the amount and allocation of Nonelective Contributions under Sections 3.3 and 5.3 for Nicor Participants, “Compensation” means, for any Plan Year, the Participant’s base pay from the Participating Companies, including vacation pay, sales commissions for sales of HVAC equipment, and military differential wage payments, but excluding (i) all other forms of compensation (such as bonuses, overtime, incentive compensation, pre-paid salary increase advances, lump sum raise payments, payments or commissions for services or products, including HVAC, sold via telemarketing and during service or repairs at a customer’s premises), and (ii) the excluded amounts described in subsection (a)(3); provided, for purposes of determining the amount and allocation of Nonelective Contributions, Compensation will be limited to the portion of the Plan Year when such Participant was a Pension-Ineligible Participant.

(c)      Section 415 and Top Heavy Compensation . Solely for purposes of Section 6.4 (relating to maximum contribution and benefit limitations under Code Section 415), and Section 15.3 (relating to minimum Contributions under a Top-Heavy Plan), “Compensation” means, with respect to a Participant for a specified period the following:

(1)      all such Participant’s wages, as defined in Code Section 3401(a) for purposes of income tax withholding at the source, that are reportable for federal income tax purposes on IRS Form W-2, but determined without regard to any rules that limit the remuneration included in wages based on the nature or location of the employment or the services performed (such as the exception for agricultural labor in Code Section 3401(a)(2)); plus

(2)      all before-tax, salary deferral or reduction contributions made to the Plan and other Code Section 401(k), Section 132(f)(4) and Section 125 plans of the Participating Companies on behalf of a Participant for such Plan Year (including any contributions made under Code Section 402(a)(8) or Section 402(h)); excluding

(3)      the amounts described in subsection (a)(3).

(d)      Key Employee and Highly Compensated Employee Compensation . Solely for purposes of determining which Employees are Key Employees and which Employees are Highly Compensated Employees for any applicable Plan Year, “Compensation” means the

Participant’s compensation as defined in Code Section 415(c), without applying the limitations of Code Section 401(a)(17). In determining the Key Employees under the Plan, the compensation of a Participant who is a nonresident alien will not include any amount that is excludable from the Participant’s gross income and is not effectively connected with the conduct of a trade or business within the United States.

(e)      Testing Compensation . For purposes of performing discrimination testing to ensure compliance with Code Section 401(a)(4), 401(k) and 401(m) and for purposes of allocating Supplemental Contributions under Section 5.4(d), “Compensation” generally means compensation as defined in Code Section 415(c) for the relevant Plan Year; provided, on a plan year-by-plan year basis, the Administrative Committee may elect to use any other definition that satisfies the nondiscrimination requirements of Code Section 414(s).

(f)      Compensation for Determining Nonelective Contributions for AGL Participants . For purposes of determining the amount and allocation of Nonelective Contributions for a Plan Year under Sections 3.3 and 5.3 for Participants other than Nicor Participants, a Participant’s Compensation means Compensation as described in subsection (a), but excluding any amounts payable during a period when the Participant was eligible to accrue benefits under the AGL Resources Inc. Retirement Plan.

1.25      Contributions means, individually or collectively, the Before-Tax, Roth, After-Tax, Matching, Nonelective, Supplemental, Rollover and Transfer Contributions permitted under the Plan.

1.26      Controlling Company means AGL Resources, Inc. a Georgia C-corporation with its principal office in Atlanta, Georgia, and its successors that adopt the Plan.

1.27      Covered Employee means an Employee of a Participating Company, other than:

(a)    An Employee who is a “leased employee” within the meaning of Code Section 414(n);

(b)    An individual classified as an independent contractor, leased employee, nonemployee or Employee of a company that is not a Participating Company under a Participating Company’s customary worker classification practices (whether or not such individual is actually an Employee of a Participating Company);

(c)    An Employee who is included in a unit of Employees covered by a collective bargaining agreement between employee representatives and one or more Participating Companies, provided that retirement benefits were the subject of good faith bargaining between employee representatives and the Participating Company or Participating Companies, unless the terms of the collective bargaining agreement require that such Employee be eligible to participate in the Plan;

(d)    An Employee who is a co-op student or intern.

1.28      Deferral Election means an election by an Active Participant directing the Participating Company of which he is an Employee to withhold a percentage of his current Compensation from his paychecks and to contribute such withheld amount to the Plan as a Before-Tax, Roth or After-Tax Contribution, pursuant to the terms of Section 3.1.

1.29      Defined Benefit Minimum means the minimum benefit level as described in Section 15.3(d).

1.30      Defined Contribution Minimum means the minimum contribution level as described in Section 15.3(c).

1.31      Defined Contribution Plan means any qualified retirement plan maintained by an Affiliate which provides for an individual account for each participant and for benefits based solely on the amount contributed to the participant’s account and any income, expenses, gains, losses and forfeitures of accounts of other participants, which may be allocated to such participant’s account.

1.32      Determination Date means the date described in Section 15.2(b)(1).

1.33      Disability or Disabled means that a Participant is (i) wholly prevented from engaging in any substantially gainful activity by reason of a medically-determinable physical or mental impairment which can be expected to result in death or to be of long-continued and indefinite duration, and (ii) determined eligible to receive long term disability benefits from a Participating Company’s long term disability plan (or if no such plan exists, determined by the Administrative Committee to meet the definition of disability under the long term disability plan of the Controlling Company). In determining whether a Participant has suffered a Disability, the Administrative Committee or its designee may require such medical proof as it deems necessary, including the certificate of one or more licensed physicians selected by the Administrative Committee. The decision of the Administrative Committee as to Disability will be final and binding.

1.34      Distributee means a Participant, a Surviving Spouse, a former Spouse who is an alternate payee under a QDRO, or a Beneficiary. For purposes of this definition, a Beneficiary does not include a Beneficiary that is not an individual, except a Beneficiary that is a trust, of which the beneficiaries are individuals or otherwise meet the requirements to be designated beneficiaries within the meaning of Code Section 401(a)(9)(E).

1.35      Effective Date means June 28, 2013, the date that this restatement of the Plan generally will be effective; provided, any effective date specified herein, for any provision, if different from the “Effective Date,” will control. The Plan initially was adopted effective as of January 1, 1986.

1.36      Elective Deferrals means, with respect to a Participant for any calendar year, the total amount of his Before-Tax Contributions plus such other amounts as determined pursuant to the terms of Code Section 402(g)(3).

1.37      Eligible Non-Highly Compensated Participant means, for a Plan Year, a Participant who (i) is not a Highly Compensated Employee, and (ii) is taken into account in performing the ADP or ACP Tests.

1.38      Eligible Retirement Plan means (i) an individual retirement account described in Code Section 408(a), (ii) an individual retirement annuity described in Code Section 408(b) (other than an endowment contract), (iii) a qualified trust described in Code Section 401(a), the terms of which permit the acceptance of rollover distributions, (iv) an annuity plan described in Code Section 403(a), (v) an annuity contract described in Code Section 403(b), (vi) an eligible plan under Code Section 457(b), which is maintained by a state, political subdivision of a state or any agency or instrumentality of a state or political subdivision of a state and which agrees to separately account for amounts transferred from the Plan, or (vii) a Roth IRA described in Code Section 408A. This definition will also apply in the case of a distribution to a Surviving Spouse, or to a Spouse or former Spouse who is the alternate payee under a qualified domestic relations order, as defined in Code Section 414(p). In the case of a distribution to a non-spouse Beneficiary, “Eligible Retirement Plan” means (i) an individual retirement account described in Code Section 408(a), (ii) an individual retirement annuity described in Code Section 408(b) (other than an endowment contract), or (iii) a Roth IRA described in Code Section 408A, in each case established for the purpose of receiving the distribution on behalf of the Beneficiary.

1.39      Eligible Rollover Distribution means any distribution to (i) a Participant, (ii) his Surviving Spouse (after his death), (iii) his Spouse or former Spouse who is his alternate payee under a qualified domestic relations order, or (iv) his Beneficiary, of all or any portion of his Account; provided, an “Eligible Rollover Distribution” will not include (A) any distribution which is one of a series of substantially equal periodic payments made, not less frequently than annually, (x) for the life (or life expectancy) of the Participant or the joint lives (or joint life expectancies) of the Participant and his Beneficiary, or (y) for a specified period of 10 years or more, (B) any distribution to the extent such distribution is required under Code Section 401(a)(9), (C) any distribution which is made upon hardship of the Participant, and (D) the portion of the distribution that is not includible in gross income, except to the extent that it is transferred (x) in a direct trustee-to-trustee transfer to a qualified trust or to an annuity contract described in Code Section 403(b), and such trust or contract provides for separate accounting for amounts so transferred and earnings thereon, including separately accounting for the portion of such distribution that is includible in gross income and the portion of the distribution which is not so includible, or (y) to an individual retirement account described in Code Section 408(a) or an individual retirement annuity described in Code Section 408(b) (other than an endowment contract). For purposes of this definition, a Beneficiary does not include a Beneficiary that is not an individual, except a Beneficiary that is a trust, of which the beneficiaries are individuals or otherwise meet the requirements to be designated beneficiaries within the meaning of Code Section 401(a)(9)(E).

1.40      Employee means any individual who is employed by an Affiliate (including officers, but excluding independent contractors and directors who are not officers or otherwise employees), including leased employees of an Affiliate within the meaning of Code Section 414(n). The term “leased employee” includes any person who is not a common-law employee of an Affiliate and who, pursuant to an agreement between an Affiliate and any other person, has performed services for an Affiliate on a substantially full-time basis for a period of at least 1 year

under the primary direction or control of the Affiliate. Notwithstanding the foregoing, if leased employees constitute 20 percent or less of an Affiliate’s nonhighly compensated work force within the meaning of Code Section 414(n)(5)(C)(ii), the term “Employee” does not include those leased employees covered by a plan described in Code Section 414(n)(5)(B).

1.41      Employment Date means, with respect to any Employee, the date on which he first completes an Hour of Service. In the case of an Employee who severs from employment with the Affiliates and is reemployed, “Employment Date” means: (i) with respect to service before the severance from employment, the date determined pursuant to the preceding sentence; and (ii) with respect to service after such reemployment, the date on which he or she first completes an Hour of Service after reemployment.

1.42      Entry Date means, with respect to a Participant, the first day of each payroll period that applies to such Participant.