No accrued benefit of a participant or beneficiary may be lower immediately after the effective date of a transfer or merger described in subsection (a) than the benefit immediately before that date.
29 U.S. Code § 1412 - Transfers between a multiemployer plan and a single-employer plan
(a) General authority
(b) Accrued benefit of participant or beneficiary not lower immediately after effective date of transfer or merger
(c) Liability of multiemployer plan to corporation where single-employer plan terminates within 60 months after effective date of transfer; amount of liability, exemption, etc.
(1) Except as provided in paragraphs (2) and (3), a multiemployer plan which transfers liabilities to a single-employer plan shall be liable to the corporation if the single-employer plan terminates within 60 months after the effective date of the transfer. The amount of liability shall be the lesser of—
(2) A multiemployer plan shall be liable to the corporation as provided in paragraph (1) unless, within 180 days after the corporation receives an application (together with such information as the corporation may reasonably require for purposes of such application) from the multiemployer plan sponsor for a determination under this paragraph—
the corporation determines that the interests of the plan participants and beneficiaries and of the corporation are adequately protected, or
fails to make any determination regarding the adequacy with which such interests are protected with respect to such transfer of liabilities.
If, after the receipt of such application, the corporation requests from the plan sponsor additional information necessary for the determination, the running of the 180-day period shall be suspended from the date of such request until the receipt by the corporation of the additional information requested. The corporation may by regulation prescribe procedures and standards for the issuance of determinations under this paragraph. This paragraph shall not apply to any application submitted less than 180 days after September 26, 1980.
A multiemployer plan shall not be liable to the corporation as provided in paragraph (1) in the case of a transfer from the multiemployer plan to a single-employer plan of liabilities which accrued under a single-employer plan which merged with the multiemployer plan, if, the value of liabilities transferred to the single-employer plan does not exceed the value of the liabilities for benefits which accrued before the merger, and the value of the assets transferred to the single-employer plan is substantially equal to the value of the assets which would have been in the single-employer plan if the employer had maintained and funded it as a separate plan under which no benefits accrued after the date of the merger.
The corporation may make equitable arrangements with multiemployer plans which are liable under this subsection for satisfaction of their liability.
(d) Guarantee of benefits under single-employer plan
(e) Transfer of liabilities by multiemployer plan to single-employer plan
In the case of a transfer described in subsection (c)(3), paragraph (1) of this subsection is satisfied by the advance agreement to the transfer by the employer who will be obligated to contribute to the single-employer plan.
(f) Additional requirements by corporation for protection of interests of plan participants, beneficiaries and corporation; approval by corporation of transfer of assets or liabilities to single-employer plan from plan in reorganization; covered transfers in connection with termination
The corporation may prescribe by regulation such additional requirements with respect to the transfer of assets or liabilities as may be necessary to protect the interests of plan participants and beneficiaries and the corporation.
No transfer to which this section applies, in connection with a termination described in section 1341a(a)(2) of this title shall be effective unless the transfer meets such requirements as may be established by the corporation to prevent an increase in the risk of loss to the corporation.
 See References in Text note below.
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