Working Past 65: Do You Really Need Medicare Yet?

Turning 65 used to mean a retirement party and a Medicare card in the same month. Not anymore. Millions of Americans are still working at 65 — by choice or by necessity — and they all hit the same question: do I sign up for Medicare now, or stay on my employer plan? Get it right and you can skip a premium you don't need yet. Get it wrong and you can pick up a penalty that follows you for life. The good news: the rules are clearer than the mail you're getting.

Before you think about premiums, plans, or paperwork, answer one question: how many people work at your company? Federal rules use that number to decide who pays your medical bills first.

• 20 or more employees: your employer's group plan is primary and Medicare would be secondary. Because your job coverage counts as "creditable" for this purpose, you're allowed to delay Part B — and its premium — without penalty for as long as you (or your spouse) keep actively working there.
• Fewer than 20 employees: Medicare is primary the month you turn 65, whether you've enrolled or not. Your small-group plan is only designed to pay after Medicare — so if you never sign up, you can be left covering Medicare's share of the bill yourself, on top of a growing Part B penalty.

The count includes full-time, part-time, and seasonal workers across all of the company's locations — so a "small" branch of a bigger employer usually still clears 20. If you're not sure, ask your HR or benefits administrator directly: "Is this plan primary or secondary to Medicare for active employees over 65?" They are required to know.

Most people who worked and paid Medicare taxes for 10 years get Part A (hospital insurance) premium-free. Since it costs nothing, most people working past 65 simply take it at 65 and let it sit behind their employer plan as backup hospital coverage. If you're already drawing Social Security, you'll be enrolled in Part A automatically.

The exception is anyone contributing to a Health Savings Account — and it's a big enough exception that it gets its own section.

IRS rules say you cannot contribute to an HSA while enrolled in any part of Medicare — including premium-free Part A. That alone surprises people. But the part that catches even careful planners is this: when you finally apply for Medicare or Social Security after 65, Part A is backdated up to six months (though never earlier than your 65th birthday month).

That retroactive start date turns HSA contributions you made during those months into excess contributions, with IRS penalties attached — even though you had no idea you were "enrolled" at the time. The fix is simple if you plan for it:

• If you're staying on a high-deductible employer plan past 65 and want to keep funding your HSA, don't enroll in any part of Medicare and don't start Social Security benefits.
• Plan to stop HSA contributions about six months before you apply for Medicare or Social Security — and prorate your final year's contribution limit for the months you were eligible.
• You can still spend the money in your HSA after enrolling in Medicare — on premiums, deductibles, copays, dental, vision, and more. Only new contributions have to stop.

Part B carries a real premium — $202.90 a month in 2026 for most people — so if your employer plan (20+ employees) is good, paying twice for the same doctor visits rarely makes sense. As long as your coverage comes from your or your spouse's current, active employment, you can wave off Part B at 65 with no penalty later.

The key word is current. The moment the employment ends — retirement, layoff, dropping to a plan-ineligible schedule — the clock starts, even if some form of coverage continues.

This is the single most expensive misunderstanding in Medicare timing. People retire, take 18 months of COBRA because it feels like continuing coverage, and discover afterward that their Special Enrollment Period expired ten months earlier. The result: waiting for the general enrollment window to add Part B, gaps in coverage, and a lifetime penalty. If you're offered COBRA at retirement, it can still make sense for dental or for a younger spouse — but enroll in Part B within your 8-month window regardless.

When the job or the group coverage ends — whichever comes first — a Special Enrollment Period opens. You have 8 months to enroll in Part B penalty-free, and coverage can start the month after you sign up, so you can time it to avoid any gap. The paperwork is two short forms:

• CMS-40B — your application for Part B (you fill this out).
• CMS-L564 — "Request for Employment Information," which your employer completes to prove you had group coverage while working. Get this signed before your last day if you can; chasing a signature from a former employer's HR office is nobody's favorite retirement activity.

Both go to Social Security — online at ssa.gov/medicare, by fax, or at your local office. Ideally, start the process about a month or two before your last day of work so Part B begins the day your group coverage stops. That timing also matters for what comes next: your first months on Part B open guaranteed-issue windows for Medigap and Medicare Advantage decisions that are much harder to unwind later.

Miss your window and the Part B late-enrollment penalty is 10% of the standard premium for every full 12-month period you went without Part B when you should have had it. It isn't a one-time fee — it's added to your premium every month, for as long as you have Part B, and it grows as the premium grows.

Two years of delay is a 20% surcharge — roughly $40 extra every month at 2026 rates, on top of the $202.90. Over a 20-year retirement that's thousands of dollars for a mistake that took one missed form. And because you can generally only sign up during the January–March general enrollment period once the SEP is gone, you may also sit months without outpatient coverage while you wait.

One more note for anyone turning 65 soon without employer coverage in the picture: your regular Initial Enrollment Period — three months before your birthday month, your birthday month, and three months after — is still the deadline that matters. The delay rules in this article only protect people with active job-based coverage.

Working past 65 doesn't force you into Medicare, and it doesn't excuse you from it either. It puts you on a decision tree with exactly three branches that matter: how big your employer is, whether an HSA is in the picture, and what you'll do in the 8 months after the job ends. Everything else is detail.

The people who get burned aren't careless — they're busy, and the rules are counterintuitive in exactly the wrong places. Nobody expects COBRA to not count, or an HSA deposit to become a tax problem retroactively. Twenty minutes mapping your dates against the rules is enough to retire on your own schedule with zero penalties. That conversation is free.

Want more plain-English guides like this? See what changed in Medicare for 2026, get ready for open enrollment, check whether you qualify for Extra Help and the Medicare Savings Programs, explore our free Medicare education center, or browse recursos en español.