Do you have to take Medicare at 65 if you are working?

Not always. If you have job-based health coverage through your own or a spouse's current employer, you may be able to delay Part B without a penalty. Most people still enroll in premium-free Part A because it usually costs nothing and can coordinate with the employer plan.

The key question is how big the employer is, because that determines which insurance pays first.

Employer size decides who pays first

• 20 or more employees: the group health plan is primary and Medicare is secondary. You can usually delay Part B while you keep that coverage.
• Fewer than 20 employees: Medicare is typically primary. In that case you generally need to enroll in Part A and Part B when first eligible, or you can be left with large uncovered bills.

Always confirm with your benefits administrator how your specific plan coordinates with Medicare before you decide to delay anything.

Your Special Enrollment Period when coverage ends

When your employment or the group coverage ends, you get an eight-month Special Enrollment Period to sign up for Part B without a late penalty. Acting during this window is how you avoid the lifelong Part B late enrollment penalty.

Do not wait until you actually need care — the coverage gap and penalties can be costly.

Two traps: HSAs and COBRA

Health Savings Accounts: once you enroll in any part of Medicare, you can no longer contribute to an HSA. If you want to keep contributing, you may need to delay all of Medicare, including premium-free Part A. Plan the timing carefully.

COBRA and retiree coverage: these usually do not count as active employer coverage for Part B. They do not give you a Special Enrollment Period, so relying on them to delay Part B can trigger a penalty. When in doubt, enroll in Part B on time.