Medicare & Employer Coverage After 65

Reaching 65 while you’re still working raises one big question: do you have to take Medicare now, or can you keep your job’s coverage and wait? The answer isn’t one-size-fits-all — it hinges on how many people your employer has. Get it right and you avoid a lifelong penalty; get it wrong and you can be left with major coverage gaps. This page is a spoke of our Working Past 65 guide.

Does Your Employer Have 20+ Employees?

The single most important factor is your employer’s size. It decides which coverage pays first (the "primary" payer) and whether you can safely delay Part B.

Employer with 20 or more employees

If you (or your spouse) are still actively working and the employer has 20+ employees, the employer plan is primary and Medicare is secondary. Because that group coverage counts as creditable coverage, you can delay Part B without a late penalty for as long as you have it. Many people in this situation take Part A and wait on Part B until they retire.

Employer with fewer than 20 employees

If the employer has fewer than 20 employees, Medicare is usually primary. That means you should enroll in both Part A and Part B at 65. If you don’t, the employer plan may pay as if you already have Medicare — leaving big gaps where neither the plan nor Medicare covers the bill. When your Medicare would have been primary, skipping Part B can be an expensive mistake. If you’re near your birthday, see turning 65 for the enrollment timeline.

Part A: Usually Yes (Unless You Have an HSA)

Regardless of employer size, almost everyone takes premium-free Part A at 65, even while working — it typically costs nothing and can help cover hospital stays as secondary coverage.

There is one important exception: if you contribute to a Health Savings Account (HSA). Enrolling in any part of Medicare — including Part A — ends your ability to make new HSA contributions. If you want to keep funding your HSA, you (and your employer, if it contributes on your behalf) often need to delay Part A too. This is a coordination detail worth getting right before your birthday.

When You Retire: Your 8-Month Window

When your active employment (or the employer coverage) ends, you get an 8-month Special Enrollment Period (SEP) to enroll in Part B with no late penalty. Learn how it works on our Special Enrollment Period page.

Important: retiree coverage and COBRA are not "active employment" coverage. They do not let you keep delaying Part B, and the clock on your 8-month SEP starts when your active job coverage ends — not when COBRA runs out. Waiting until COBRA ends can leave you with a permanent Part B late penalty and a gap in coverage.

Talk It Through Before You Decide — Free

Employer size, HSAs, and enrollment timelines are easy to get wrong, and the penalties last a lifetime. Call us free at 435-219-5120 (TTY: 711) and we’ll look at your specific situation — your employer’s size, your HSA, and your retirement date — so you enroll at the right time with no penalty. Start with the Working Past 65 hub if you’d like the full picture first.