This regulatory action prescribes rules related to the tax imposed by 26 U.S.C. 5000D. Section 5000D(a) imposes a tax on the sale of a designated drug by the manufacturer, producer, or importer of such drug during a day described in section 5000D(b). The section 5000D tax is a component of a prescription drug price negotiation program administered by the Centers for Medicare and Medicaid Services (CMS) (the Program). See sections 119198 of the Social Security Act. Under the Program, CMS selects a small number of single-source drugs for price negotiation, with the intention of agreeing on a "maximum fair price” for each selected drug for purposes of Medicare. This regulatory action is aligned with Executive Order 14273, Lowering Drug Prices by Once Again Putting Americans First (Apr. 15, 2025) because it provides rules relating to this "maximum fair price.”