Guide
Medicare with retiree, COBRA or a spouse's job coverage
Other coverage changes the Medicare rules, and not always the way people expect. Retiree plans and COBRA usually pay after Medicare, and neither lets you delay Part B without a penalty. A working spouse's plan often does. Here's how each works.
Last reviewed October 26, 2026. General information, not advice about any plan.
Who pays first
- Retiree coverage
- Medicare pays first; the retiree plan pays second.
- COBRA
- Medicare pays first if you have Medicare because of age or disability; COBRA may pay only a small part. (With ESRD, COBRA pays first for up to 30 months.)
- A spouse's current job, 20+ employees
- The job's plan pays first; Medicare pays second.
- A spouse's current job, under 20 employees
- Medicare pays first, and the plan may not pay without Part A and Part B.
Retiree coverage
Retiree plans usually expect you to have Part A and Part B, and may not pay for any time you could have had Medicare but didn't. Employers and unions don't have to keep offering retiree coverage, and can change or end it.
- Joining a Medicare Advantage or Part D plan can make you lose your retiree coverage, sometimes including health benefits for your spouse and dependents, and you may not get it back. Call your benefits administrator before you join any plan.
- Retiree coverage doesn't give you a special window to sign up for Part B late without a penalty.
COBRA
- Part B timing
- Your 8-month window to sign up for Part B starts when you stop working, not when COBRA ends. Don't wait for COBRA to run out.
- Already on COBRA, then Medicare
- Your COBRA will probably end when you sign up for Medicare.
- Drug coverage
- If your COBRA includes creditable drug coverage, you get a window to join Part D without a penalty when it ends.
A working spouse's plan
If you're covered through your spouse's current job at an employer with 20 or more employees, you can usually wait on Part B. You then have 8 months to sign up, starting when your spouse stops working or the coverage ends, whichever comes first. To avoid a gap, sign up the month before your spouse retires.
This doesn't apply to COBRA, retiree, severance or Marketplace coverage, or to an employer with fewer than 20 employees.
The creditable coverage letter
Employer, union and retiree plans must tell Medicare-eligible members each year, before October 15, whether their drug coverage is creditable, meaning expected to pay at least as much as standard Medicare drug coverage. Keep these letters. If you ever need to show you didn't go without drug coverage, they're your proof. Unsure what your coverage means for you? A licensed agent or your state's free SHIP can walk through it; the turning-65 checklist has the timeline.
Common questions
Do I need Part B if I have retiree coverage?
Usually yes. Medicare pays first, and retiree plans may not pay for services if you don't have Part A and Part B. Retiree coverage also doesn't give you a special window to sign up for Part B later without a penalty.
Can I wait until COBRA ends to sign up for Part B?
No. Your 8-month window to sign up for Part B starts when you stop working, whether or not you take COBRA. Waiting for COBRA to end can mean a gap in coverage and a lifelong penalty.
Will joining a Medicare Advantage plan affect my retiree benefits?
It can. Joining a Medicare Advantage or drug plan might make you, your spouse and your dependents lose retiree coverage, and you may not get it back. Call your benefits administrator first.
What is a notice of creditable coverage?
A yearly letter from your employer, union or retiree plan saying whether its drug coverage is at least as good as Medicare's. Keep it: it shows you can delay Part D without a penalty.
Keep reading
- Turning 65: a Medicare checklist, month by monthWhat to do before and after your 65th birthday: when to sign up, what to do if you're still working, your one-time Medigap window, and the deadlines that carry lifelong penalties.
- Medicare late enrollment penalties: how they work and how to avoid themHow the Part B, Part D and Part A penalties are figured, with 2026 examples, the situations that let you sign up late without one, and how to challenge a penalty you think is wrong.
- Medicare with VA or TRICARE benefits: what veterans should knowShould a veteran with VA health care sign up for Part B? How TRICARE For Life works with Medicare, whether you need a drug plan, and what to check before joining a Medicare Advantage plan.
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