medicare part a while working is one of the few Medicare questions where the right answer is genuinely personal. Part A is usually premium-free at 65. That makes it look like free money. But if you contribute to a Health Savings Account, Part A is not free at all. Enrolling ends your HSA eligibility permanently. So the decision about medicare part a while working really turns on one question: do you still want to fund an HSA?
- The Rule Behind Medicare Part A While Working
- Your Choices at 65
- The Penalty If You Get It Wrong
- Medicare Part A While Working: the Paperwork
- The Traps People Fall Into
- Frequently Asked Questions
- Key Takeaways: Medicare Part A While Working
- Compare Your Options
- Official Sources & Resources
- Related Guides
This guide walks through how the rules interact. It covers employer size, the forms, the penalties and the timing traps. Nothing here is legal or tax advice. It describes the process so you can ask better questions of your employer and Social Security.
The Rule Behind Medicare Part A While Working
Medicare does not force you off an employer plan at 65. What changes is who pays first. Those are the Medicare Secondary Payer rules, explained by CMS at Medicare Secondary Payer.
The dividing line is 20 employees. If your employer has 20 or more employees, the group health plan pays first. Medicare pays second. Your coverage based on current employment stays primary, so delaying Part B is normally safe.
If your employer has fewer than 20 employees, Medicare generally pays first. The group plan pays second. Some small-employer plans will not pay much at all until Medicare is in place. Medicare explains the order of payment at Who pays first?.
Multi-employer plans are a separate case. If any one employer in the arrangement has 20 or more employees, the plan can still pay primary. Ask your plan administrator in writing which rule applies to you.
Your Choices at 65
There are three realistic paths. Take Part A only and keep the employer plan. Take Part A and Part B together. Or delay all of Medicare and keep contributing to your HSA.
Path three only works if your employer plan is primary. That means 20 or more employees and coverage based on current employment.
| Your situation | Who pays first | What to do |
|---|---|---|
| Employer with 20+ employees, no HSA contributions | Employer plan pays first, Medicare second | Premium-free Part A is usually harmless. Part B can wait. |
| Employer with 20+ employees, still funding an HSA | Employer plan pays first, Medicare second | Delaying all of Medicare keeps HSA eligibility. Confirm the plan is primary in writing. |
| Employer with fewer than 20 employees | Medicare generally pays first | Enrolling in Part A and Part B at 65 is usually expected. HSA contributions must stop. |
| Multi-employer plan, one employer has 20+ | Plan may pay first | Get the plan administrator’s written answer before deciding. |
| COBRA or retiree coverage only | Medicare pays first | This is not current employment coverage. Enroll on time. |
Note what the table does not say. It does not say medicare part a while working is always a good idea. If the HSA matters more than the secondary hospital coverage, delaying is a legitimate choice.
The Penalty If You Get It Wrong
Two penalties matter here, and both can last for life. Medicare describes them at Avoid late enrollment penalties.
The Part B penalty is 10 percent of the standard premium. You add 10 percent for each full 12-month period you could have had Part B but did not. CMS set the 2026 standard Part B premium at $202.90 in its 2026 Medicare Parts A and B Premiums and Deductibles fact sheet.
So two full years late is 20 percent. At the 2026 standard premium, that is roughly $40 added each month. You pay it for as long as you hold Part B.
The Part D penalty works differently. It is 1 percent of the national base beneficiary premium for each full month you went without creditable drug coverage. That base amount changes annually, so confirm the current figure with Medicare or your plan before doing the math.
Twenty-four uncovered months means a 24 percent penalty. The penalty is recalculated each year as the base premium moves. It continues for as long as you have Part D.
Delaying Part B while covered by a large employer plan does not trigger these penalties. The Special Enrollment Period exists for exactly that reason.
Medicare Part A While Working: the Paperwork
The Special Enrollment Period runs for eight months. It starts the month after employment ends or the group coverage ends, whichever comes first. SSA describes the process at Sign up for Part B only.
Two forms do the work. The first is Form CMS-40B, Application for Enrollment in Medicare Part B. You sign that one yourself.
The second is Form CMS-L564, Request for Employment Information. Your employer or the plan administrator signs it. It proves your coverage was based on current employment.
Send both forms together to Social Security. Do not wait until the last week. Employers can be slow returning CMS-L564, and the eight-month window does not pause for them.
If your employer will not complete the form, SSA can accept other evidence. Pay stubs, W-2s and health plan cards are examples. Ask your local office what it will accept in your case.
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Anyone handling medicare part a while working through the Special Enrollment Period should keep copies of everything. Note the date you submitted and the office that received it.
The Traps People Fall Into
The biggest trap is retroactive Part A. When you apply after 65, Part A can be backdated up to six months. It never goes back before the month you turned 65.
That backdating is what wrecks HSA contributions. IRS Publication 969 is clear that your contribution limit is zero beginning the first month you are enrolled in Medicare. Retroactive months count.
The common workaround is to stop HSA contributions six months before you apply. Excess contributions get reported on Form 8889 and can face an excise tax each year they stay in the account. Ask a tax preparer to run your specific months.
Claiming Social Security is the second trap. Social Security enrollment brings Part A with it automatically. You cannot keep the retirement benefit and refuse premium-free Part A.
COBRA is the third. COBRA is not coverage based on current employment. Your Special Enrollment Period is already running while you use it.
Retiree coverage behaves the same way. So does a small employer plan. In both cases, delaying can leave you paying claims Medicare would otherwise have covered.
Frequently Asked Questions
Can I keep my HSA if I take Part A?
You keep the account and can spend the balance. You cannot make new contributions. That applies to your money and your employer’s money alike.
Is premium-free Part A ever a bad deal?
Yes, if you are funding an HSA. The lost tax-advantaged contributions can outweigh the secondary hospital coverage. Weighing medicare part a while working against HSA contributions is the whole decision.
Who signs CMS-L564?
Your employer or plan administrator signs it. You sign CMS-40B. Both go to Social Security together.
What if I already contributed after Part A started?
Talk to a tax preparer promptly about withdrawing the excess and correcting the return. Do not guess at the correction yourself, and confirm your exact enrollment start date with Social Security first.
Key Takeaways: Medicare Part A While Working
- Employer size decides everything. Whether medicare part a while working is a choice or a requirement turns on the 20-employee rule.
- Part A is usually free. Most people take it at 65 even when medicare part a while working lets them delay Part B.
- Except with an HSA. Part A ends HSA contributions, the one case where medicare part a while working means delaying Part A too.
- COBRA does not count. For medicare part a while working, COBRA is not active employer coverage, and assuming otherwise creates a lifetime penalty.
- The penalty never ends. The Part B penalty from a medicare part a while working mistake is added to every premium for life.
- Keep the creditable coverage letter. It is the proof that medicare part a while working did not leave a gap in drug coverage.
Compare Your Options
Once you know what medicare part a while working means for you, the official Plan Finder shows what is actually sold in your ZIP code, and a SHIP counselor will walk it with you for free — no commission, no sales call.
Official Sources & Resources
- Social Security — Medicare enrollment: https://www.ssa.gov/medicare
- IRS Publication 969 (HSAs): https://www.irs.gov/publications/p969
- Medicare.gov: https://www.medicare.gov
- CMS.gov: https://www.cms.gov
- Find your SHIP counselor: https://www.medicare.gov/talk-to-someone
Checked against the official sources above in September 2026. Rules and dollar figures change; if a notice you received disagrees with this page, the notice wins — and please tell us. General information, not legal, financial or medical advice.