29 U.S.C. § 1381: Withdrawal liability established; criteria and definitions

If an employer withdraws from a multiemployer plan in a complete withdrawal or a partial withdrawal, then the employer is liable to the plan in the amount determined under this part to be the withdrawal liability. first, by any de minimis reduction applicable under section 1389 of this title , next, in the case of a partial withdrawal, in accordance with section 1386 of this title , then, to the extent necessary to reflect the limitation on annual payments under section 1399(c)(1)(B) of this title , and finally, in accordance with section 1405 of this title . The term “complete withdrawal” means a complete withdrawal described in section 1383 of this title . The term “partial withdrawal” means a partial withdrawal described in section 1385 of this title . Any withdrawal liability incurred by an employer pursuant to part 1 of subtitle E of title IV of the Employee Retirement Income Security Act of 1974 ( 29 U.S.C. 1381 et seq.) as a result of the complete or partial withdrawal of such employer from a multiemployer plan before September 26, 1980 , shall be void. Any amounts paid by an employer to a plan sponsor as a result of such withdrawal liability shall be refunded by the plan sponsor to the employer with interest (in accordance with section 401(a)(2) [ 26 U.S.C. 401(a)(2) ]), less a reasonable amount for administrative expenses incurred by the plan sponsor (other than legal expenses incurred with respect to the plan) in calculating, assessing, and refunding such amounts. The amendments made by this section [amending sections 1391, 1397, 1399, 1415 and 1461 of this title and provisions set out as a note under section 1385 of this title ] shall not be construed to increase the liability incurred by any employer pursuant to part 1 of subtitle E of title IV of the Employee Retirement Income Security Act of 1974 ( 29 U.S.C. 1381 et seq.), as in effect immediately before the amendments made by subsection (b) [amending sections 1391, 1397, 1399, 1415, and 1461 of this title and provisions set out as a note under section 1385 of this title ], as a result of the complete or partial withdrawal of such employer from a multiemployer plan prior to September 26, 1980 . In the case of an employer who, on September 26, 1980 , has a binding agreement to withdraw from a multiemployer plan, subsection (a)(1) shall be applied by substituting ‘ December 31, 1980 ’ for ‘ September 26, 1980 ’.”