What is the Medicare secondary payer law?


Editorial team Published on

Medicare Secondary Payer (MSP) rules set which health insurance pays first when a person has Medicare and another type of insurance.

You can review official guidelines and coordination details directly through the Centers for Medicare & Medicaid Services.

When Medicare is Secondary (Pays Second)

Medicare pays after these primary insurance plans:

  • Working Aged (65 or older): Group health plans from an employer with 20 or more employees if you or your spouse are actively working.
  • Disability (under 65): Group health plans from an employer with 100 or more employees.
  • End-Stage Renal Disease (ESRD): Group health plans for a 30-month coordination period starting when you become eligible for Medicare.
  • Accidents and Injuries: Workers' compensation, no-fault insurance, and liability insurance.

When Medicare is Primary (Pays First)

Medicare pays first under these conditions:

  • Small Employers: Group health plans from employers with fewer than 20 employees (for age 65+) or fewer than 100 employees (for disabilities).
  • Retiree Coverage: Insurance plans you receive after retirement.
  • Medicaid: Medicare is always primary over Medicaid.

Conditional Payments

  • If your other insurance does not pay a claim within 120 days, Medicare may make a temporary "conditional payment" to cover the bill.
  • You or your primary insurer must repay Medicare once the primary insurance settles the claim.