Working past 65: when to take Medicare and when to wait
How employer size affects whether Medicare pays first, HSA contribution rules, the Part B Special Enrollment Period, and a checklist for leaving work.
More people now work past 65. Whether you should enroll in Medicare right away depends on the size of your employer, your plan, and whether you contribute to a Health Savings Account.
Employer size decides who pays first
| Employer size | Who pays first | Usual approach |
|---|---|---|
| 20 or more employees | Employer plan | Many people take premium-free Part A and delay Part B |
| Fewer than 20 employees | Medicare | Enroll in Parts A and B at 65; the employer plan pays second |
If Medicare is primary and you skip Part B, your employer plan may pay as if Medicare had paid, leaving you with large bills.
HSAs and Medicare
You cannot contribute to a Health Savings Account once any part of Medicare starts, including premium-free Part A. Part A can be backdated up to six months when you sign up after 65, so stop HSA contributions six months before you plan to enroll, to avoid excess contributions. You can keep spending your HSA balance on qualified expenses, including Medicare premiums.
Leaving work
When your job or employer coverage ends, you have an 8-month Special Enrollment Period for Part B and a 63-day window to get Part D without penalty. Your Medigap open enrollment starts when Part B begins.
Checklist: 1. Ask HR for a creditable coverage letter for drugs (Part D) and proof of group coverage (form CMS-L564). 2. Apply for Part B one to two months before coverage ends, so there is no gap. 3. Choose Medigap and Part D, or Medicare Advantage, to start the same day.
COBRA is not a substitute
COBRA does not count as current-employment coverage for Part B. If you take COBRA instead of Part B after leaving work, you can face a Part B penalty and a coverage gap; see the penalty explained.
Questions people ask
Do I need Part B if I am still working?
If your employer has 20 or more employees and you have its group plan, you can usually delay Part B without penalty.
Can I contribute to an HSA on Medicare?
No. Contributions must stop when any Medicare coverage begins, including backdated Part A.
What happens when I retire?
You get an 8-month Special Enrollment Period for Part B.
Does COBRA count?
Not for avoiding the Part B penalty.
Independent educational site. Not affiliated with or endorsed by the U.S. government, the federal Medicare program, or any insurance company. Figures are 2026 amounts published by CMS unless noted; check Medicare.gov for your situation.