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Do I need Part B if I'm still working at 65?
Last checked October 5, 2026 against the official rules. Sources are listed at the end.
Usually not, if you (or your spouse) are still working and covered by that job's health plan, and the employer has 20 or more employees. You can sign up later without a penalty. If the employer is smaller, or your coverage is COBRA or a retiree plan, sign up at 65.
The rule in one sentence
You can put off Part B without a penalty while you have health coverage from a job you or your spouse still has, at an employer with 20 or more employees.
That's it. Both parts matter. The coverage has to come from current work, and the employer has to be big enough.
When you can wait
- You're still working at 65 and on your employer's health plan, and the company has 20 or more employees.
- You're on your spouse's health plan from their current job, at an employer with 20 or more employees.
In these cases the job plan pays your bills first, so Part B isn't needed yet. Many people still sign up for Part A at 65 because it's usually free, unless they put money into a Health Savings Account (see Medicare and your HSA).
When you can't wait
- The employer has fewer than 20 employees. Medicare pays first and the job plan pays second. If you don't have Part B, the job plan may refuse to pay much of the bill.
- You have COBRA. COBRA isn't coverage from current work, so it doesn't let you wait. See COBRA and Medicare.
- You have a retiree plan from a former employer. Same problem: it isn't current work.
- You bought your own plan, for example through healthcare.gov.
In all of these, sign up during your sign-up window: the 7 months around your 65th birthday. If you miss it, you can only sign up January through March, which can leave you without coverage for months. And if a full year or more goes by without Part B, you'll pay a penalty every month for as long as you have it.
When the job ends: your 8-month window
Once the job or the job's coverage ends (whichever comes first), you have 8 months to sign up for Part B with no penalty. The 8 months start the month after it ends.
Don't use all 8 months. Sign up before your job coverage ends so Part B starts the next month and you have no gap in coverage.
Example. Linda turns 65 in April 2027 but keeps working at a large company until December 2028.
She can skip Part B at 65. She signs up between September and December 2028, so Part B starts January 1, 2029. Her penalty-free window would have lasted through August 2029, but signing up early means no gap.
The form that protects you
When you sign up late, Social Security needs proof that you had job coverage the whole time. That proof is Form CMS-L564, which your employer fills out. Send it with your Part B sign-up, which you can do online at ssa.gov or by mail with Form CMS-40B.
Ask HR for the CMS-L564 two to three months before you stop working. It can take them a while.
Don't forget drug coverage
If your job plan includes drug coverage that's "creditable" (at least as good as Medicare's), you can also wait on Part D. Your plan sends a letter each year saying whether it is. Keep those letters. When the job coverage ends, join a drug plan within 63 days to avoid the Part D penalty.
See your own sign-up dates
Enter your birthday and your job's coverage. We'll show when to sign up, when coverage starts, and your penalty-free window.
Sources
- Medicare.gov: Working past 65
- Medicare.gov: When can I sign up for Medicare?
- CMS Form CMS-L564 (Request for Employment Information)
- CMS Form CMS-40B (Application for Enrollment in Part B)
This guide explains the general rules. It isn't legal, tax or insurance advice, and your situation may differ. Settled Years doesn't sell insurance or take commissions.