What are MSP rules in Medicare?

• A. They determine patient co-pay amounts.
• B. They apply only to Part D.
• C. Medicare Secondary Payer rules determine when another payer is primary and how payment is coordinated when multiple payers exist.
• D. They set annual enrollment periods.

Answer: (C)

MSP rules govern how Medicare interacts with other health coverage when more than one payer is involved. They decide which payer pays first (which one is primary) and how Medicare coordinates with that payer to handle remaining costs. This prevents double payments and ensures the correct sharing of costs when someone has multiple sources of coverage, such as an employer health plan, Medicaid, workers’ comp, or auto liability coverage. MSP rules apply broadly to how payments are coordinated, not to setting co-pays or enrollment periods.