When you have Medicare and employer insurance, one pays first and the other may help with what remains. The first is called the primary payer; the second is the secondary payer. Having both does not guarantee that every bill will be paid in full.

Coverage From Current Employment

For someone 65 or older:

  • An employer group plan generally pays first when the employer has 20 or more employees.
  • Medicare generally pays first when the employer has fewer than 20 employees.

For disability-based Medicare before 65, a qualifying large group health plan generally pays first at 100 or more employees; Medicare generally pays first below that threshold. Do not apply the age-65 threshold of 20 to this group.

Plans covering more than one employer, End-Stage Renal Disease (ESRD), workers’ compensation, and other situations have separate rules. ESRD means permanent kidney failure requiring dialysis or a transplant. If you have ESRD, ask the employer plan and Medicare: “When does my coordination period begin and end, and which payer is primary during each month?” See the ESRD rules.

Retiree and COBRA Coverage

Medicare generally pays before retiree coverage. Retiree insurance may require enrollment in both Part A and Part B before it pays fully.

COBRA generally pays after Medicare for people eligible because of age. COBRA does not extend the eight-month Part B Special Enrollment Period tied to active employment.

Protect Employer Benefits

Before joining Part D or a Medicare Advantage plan, ask whether doing so would cause you, a spouse, or dependents to lose employer or union coverage. Lost retiree coverage may be impossible to recover.

Also ask whether employer drug coverage is creditable for Part D, meaning it is expected to pay at least as much as standard Medicare drug coverage.

Keep Medicare Updated

Tell providers about every form of insurance. If coverage changes, notify Medicare's Benefits Coordination & Recovery Center so bills are sent to the right insurer first.

Use Medicare's coordination-of-benefits tool for your specific situation.

When reporting a change, have both insurance cards, employer details, and employment and coverage start/end dates ready. Contact the Benefits Coordination & Recovery Center to report coverage changes and ask how to correct a claim sent to the wrong primary payer.

Medicare policy sources last checked: October 8, 2026.