1. Short title This Act may be cited as the Susan Muffley Act of 2023 . 2. Guaranteed benefit calculation for certain plans (a) In general (1) Increase to full vested plan benefit (A) In general For purposes of determining what benefits are guaranteed under section 4022 of the Employee Retirement Income Security Act of 1974 (in this section referred to as ERISA ) with respect to an eligible participant or beneficiary under a covered plan specified in paragraph (4) in connection with the termination of such plan, the amount of monthly benefits shall be equal to the full vested plan benefit with respect to the participant. (B) No effect on previous determinations Nothing in this Act shall be construed to change the allocation of assets and recoveries under sections 4044(a) and 4022(c) of ERISA as previously determined by the Pension Benefit Guaranty Corporation (in the section referred to as the corporation ) for the covered plans specified in paragraph (4), and the corporation’s applicable rules, practices, and policies on benefits payable in terminated single-employer plans shall, except as otherwise provided in this section, continue to apply with respect to such covered plans. (2) Recalculation of certain benefits (A) In general In any case in which the amount of monthly benefits with respect to an eligible participant or beneficiary described in paragraph (1) was calculated prior to the date of enactment of this Act, the corporation shall recalculate such amount pursuant to paragraph (1), and shall adjust any subsequent payments of such monthly benefits accordingly, as soon as practicable after such date. (B) Lump-sum payments of past-due benefits Not later than 180 days after the date of enactment of this Act, the corporation, in consultation with the Secretary of the Treasury and the Secretary of Labor, shall make a lump-sum payment to each eligible participant or beneficiary whose guaranteed benefits are recalculated under subparagraph (A) in an amount equal to— (i) in the case of an eligible participant,