On March 11, 2021, the Centers for Medicare & Medicaid Services (CMS) released the updated State Phased-Down (SPD) Billing Guide. The Medicare Prescription Drug Improvement and Modernization Act of 2003 (Medicare Modernization Act or MMA) established the Medicare Part D prescription drug benefit. As a result, Medicare became the primary payer for most prescription drugs for full-benefit dually eligible individuals. However, the MMA also established the phased-down state contribution process, in which states make monthly payments to CMS for a portion of those prescription drug expenditures. The new guide incorporates changes in response to comments on the draft version available for public comment in December 2020, updating information and instructions for states on a range of phased-down contribution processes.