NEW YORK, May 21, 2026 – Proskauer secured a unanimous victory at the U.S. Supreme Court on behalf of the Trustees of the IAM National Pension Fund. In a 9-0 decision authored by Justice Ketanji Brown Jackson, the Court resolved a circuit split concerning how multiemployer pension plans calculate the liability of withdrawing employers. That calculation depends on assumptions selected by a plan’s actuary about the plan’s anticipated experience, including the rate of return the plan will receive on its investments and how long participants will live and collect benefits. In its decision, the Court held that ERISA does not impose a deadline on actuaries to select those assumptions before the end of the plan year. In so ruling, the Court rejected a decision by the Second Circuit that had imposed such a deadline.
The decision carries significant consequences for multiemployer pension plans nationwide. Proskauer convinced the Supreme Court that the timing constraints urged by the petitioners in the case would distort withdrawal liability calculations and undermine ERISA’s design by forcing plans to rely on outdated assumptions. The Court’s decision preserves actuarial flexibility and ensures the accuracy of withdrawal-liability calculations, which are critical to the solvency of multiemployer plans.
“We are pleased that the Court recognized what actuaries and pension plans have understood for decades – that ERISA permits actuaries to select assumptions after the end of a plan year to ensure that withdrawal liability calculations most accurately reflect a plan’s condition,” said John E. Roberts, co-chair of Proskauer’s Appellate Practice Group, who argued the case. “The Court’s unanimous decision preserves the integrity of the withdrawal-liability framework Congress enacted and brings needed clarity and uniformity to an issue of substantial importance to multiemployer pension plans.”
The Proskauer team was led by partner John Roberts (Appellate) and included partner Myron Rumeld (ERISA Litigation), partner Anthony Cacace (Compensation & Benefits), partners Lena Hughes and Mark Harris (Appellate), senior counsel Neil Shah (Compensation & Benefits), and senior counsel Lucas Kowalczyk (Appellate).
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