Medicare if you keep working past 65: what to sign up for, and when

Why employer size matters

When you have both Medicare and a job-based plan, one pays first and the other pays second. The size of the employer decides which.

How employees are counted

20 or more employees on each working day in at least 20 weeks of this year or last year.

Union and multi-employer plans

They count as 20+ if any employer in the plan has 20 or more employees, unless the plan asks Medicare for a small-employer exception. Ask the plan.

Self-employed, or a plan not offered to everyone

Ask whether it counts as employer group health coverage. If it doesn't, sign up at 65 to avoid the Part B penalty.

Whatever the size, ask the employer's benefits office in writing whether you need Part A and Part B when you turn 65. Some plans require them.

Part A while you work

Most people get Part A without a premium, so many sign up at 65 even while working: it can pay some hospital costs the job plan doesn't. But if you or your employer put money into an HSA, Part A ends those contributions. If you qualify for premium-free Part A, you can sign up any time after you turn 65. Two catches:

It's backdated

When you sign up after 65, Part A starts up to 6 months before the month you apply, but never before the month you turn 65.

Social Security brings Part A with it

If you start Social Security retirement benefits, you get Part A too. You can't keep the benefits and turn Part A down.

Part B is separate

Applying for Social Security at or after 65 doesn't sign you up for Part B automatically; you choose it on the application. How to sign up.

If you have an HSA

You can't put money into a health savings account for any month you have Medicare, and that includes the months Part A is backdated. Money already in the account is still yours to spend, including on Part B, Part D and Medicare Advantage premiums (but not Medigap premiums).

If your birthday is on the 1st, your Medicare can start a month earlier; check the date on your card.

• Contributions for Medicare months are excess contributions. Take them out, plus any earnings on them, by your tax-filing deadline (including extensions), or pay a 6% tax for each year they stay. Ask a tax professional.
• Tell your employer the month to stop, since their contributions count too.

Coverage that doesn't count

These don't let you delay Part B without a penalty, even if they feel like job coverage:

COBRA

Your 8 months start when the job ends, not when COBRA ends. COBRA and retiree coverage.

Retiree coverage

Medicare pays first, and the retiree plan may not pay without Part A and Part B.

Severance or layoff coverage

Coverage from a former employer isn't current employment.

VA coverage, or a Marketplace or individual plan

Not job-based. Marketplace premium help also stops once you can get premium-free Part A.

Drug coverage

If your job plan's drug coverage is "creditable" (at least as good as Medicare's), you can wait to join a Medicare drug plan without a penalty. The plan has to tell you every year, usually in a fall letter. Keep those letters.

When the job coverage ends

You have until 2 months after the month it ends to join a drug plan or a Medicare Advantage plan with drug coverage. That also applies when COBRA ends.

The 63-day rule

Going 63 days or more in a row without creditable drug coverage can mean a penalty for as long as you have Medicare drug coverage.

Check first

Joining a Medicare drug plan can end your job or union health coverage, for you and your family.

When you stop working

You can sign up for Part B any month you still have the job coverage, or during the 8 months after the job or the coverage ends, whichever comes first. If you don't use that window, you'll generally have to wait for the General Enrollment Period (January 1 to March 31), go without Part B until then, and may owe a lifelong penalty.

1. 1

   About 2 months before the job ends

   Ask the employer to fill in Section B of form CMS-L564, which confirms your coverage dates. If they can't or won't, fill it in yourself without signing it and attach proof: pay stubs or W-2s showing health premiums, insurance cards with dates, or a letter or email from the employer or plan.
2. 2

   The month before the coverage ends

   If you already have Part A, apply for Part B online at SSA.gov/medicare/sign-up, or mail or fax form CMS-40B with the CMS-L564 to your local Social Security office. If you don't have Part A yet, apply for both online or call Social Security at 1-800-772-1213 (TTY 1-800-325-0778), and include the CMS-L564. Signing up while still covered, or in the first full month after, lets you pick a start date: the first of that month or of any of the next 3.
3. 3

   Choose the rest of your coverage

   You have 2 months after the job coverage ends to join a drug plan or Medicare Advantage plan. Your 6-month Medigap Open Enrollment Period starts the month Part B starts, not at 65. Advantage or Medigap?
4. 4

   Tell Medicare the job coverage ended

   Call 1-800-MEDICARE so Medicare pays first from then on.

A Part D creditable-coverage letter doesn't prove job health coverage for Part B. Keep both. A licensed agent or your state's free SHIP counselor can walk you through the timing; which to call.

Common questions

Keep reading

• Medicare with retiree, COBRA or a spouse's job coverageWho pays first, whether you need Part B, and the mistakes that cost people their retiree benefits or a lifelong penalty. For anyone with retiree coverage, COBRA, or a working spouse's plan.
• How to sign up for Medicare Part A and Part B, step by stepWhether you'll be signed up automatically, when to apply, how to apply online, by phone or in person, when coverage starts, and what to choose next.
• 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.