A Practice Note providing a general overview of multiemployer pension plans and explaining the rules governing them under the Employee Retirement Income Security Act of 1974 (ERISA) and the Internal Revenue Code (Code). Multiemployer plans are maintained under one or more collective bargaining agreements (CBAs) between one or more employee organizations (usually a union) and more than one employer. This Note also outlines the funding and qualification rules specific to multiemployer pension plans and provides a summary of withdrawal liability rules. Additionally, this Note summarizes special rules for suspending benefits in severely underfunded plans and procedures for the Pension Benefit Guaranty Corporation (PBGC) to facilitate mergers and partitions of plans.