M & K Employee Solutions, LLC, et al., Petitioners v. Trustees of the IAM National Pension Fund

This case was about withdrawal liability, money an employer may owe after leaving a multiemployer pension plan. The dispute concerned how the IAM National Pension Fund calculated that amount under federal pension law. The key issue was whether calculations must use actuarial assumptions accepted at year's end or later-adopted assumptions. The Court's full reasoning is not yet available. The case was argued on January 20, 2026, after the Court agreed to review it. This matters because withdrawal liability can depend on predictions about future assets, liabilities, and interest rates. The answer could affect how much withdrawing employers must pay pension funds.

This case affects employers leaving multiemployer pension plans and workers relying on those pensions. For example, a company that exits a shared plan may owe withdrawal liability (its share of underfunding). The size of that bill can affect business costs and pension funding. The dispute is over how to calculate that amount at the end of the prior plan year. The Court is reviewing whether plans must use assumptions in place then or later-adopted assumptions. Those assumptions include projected liabilities, assets, interest rates, and other predictions. The eventual answer could shape future pension-withdrawal disputes and planning.

Not official Court text.