“An employer that stops participating in an underfunded Multiemployer Pension Plan must pay the plan ‘withdrawal liability’ — i.e., its share of the plan’s unfunded vested benefits. Calculating the unfunded vested benefits is a complicated endeavor because the plan’s actuary must predict the value of the plan’s future assets and obligations. To do so, the actuary makes certain assumptions about, for example, retirees’ life expectancies and the anticipated growth rate of the plan’s investments. By statute, an employer’s withdrawal liability is based on the value of the plan’s unfunded vested benefits ‘as of’ the last day of the plan year preceding the employer’s withdrawal, also known as the measurement date. The question presented in this case is whether the ‘as of’ language sets the measurement date as the deadline by which actuaries must select the assumptions that underlie the withdrawal-liability calculation. The Court of Appeals for the D. C. Circuit held that it does not, concluding that actuaries may select their assumptions after the measurement date. We agree. The statute governing the selection and use of actuarial assumptions in the withdrawal-liability context contains no requirement that actuaries use assumptions adopted prior to the measurement date.”

 

M&K Employee Solutions v. Trustees of IAM National Pension Fund, 146 S.Ct. 1224 (2026).