Medicare When You Are Still Working: The Employer Size Rules That Change Everything

Turning 65 while still working creates one of the more complex Medicare decisions you will face. The conventional wisdom that you must take Medicare at 65 or face penalties is not quite right, but neither is assuming your employer coverage automatically protects you. The rules turn on a single factor most people do not think to check: how many employees your employer has. Getting this wrong costs money in two different directions.

Bryce's Take

The employer size question is the first thing I ask anyone who calls me at 65 and is still working. People assume their coverage protects them regardless of company size. It does, but only if the employer has 20 or more employees. Call your HR department and ask exactly how many people are employed before you make any Medicare enrollment decisions.

The 20-employee rule that determines everything

When you have employer health coverage through your own or your spouse's active employment, Medicare coordinates with that coverage based on employer size. If the employer has 20 or more employees, the employer plan is primary and Medicare is secondary. You can delay Medicare Part B without penalty as long as this qualifying employer coverage remains active. If the employer has fewer than 20 employees, Medicare is primary, meaning Medicare pays first and the small employer plan fills gaps. In this case, you must have Medicare for your coverage to work properly, and delaying Part B creates genuine coverage problems.

What primary and secondary means in practice

When your employer plan is primary, it pays first up to its coverage limits. Medicare then pays some or all of what the employer plan did not cover, potentially reducing your total out-of-pocket costs significantly. When Medicare is primary (small employer situation), the employer plan only pays after Medicare has paid. If you are not enrolled in Medicare and your employer plan is secondary to Medicare, you may receive very little benefit from the employer plan for certain services.

Spouse's employer coverage counts

You do not need to be the covered employee yourself. If your spouse is actively employed at a company with 20 or more employees, and you are covered under their employer health plan, that coverage qualifies as the basis for delaying Medicare. The key word throughout is active employment. Coverage from a retired spouse, COBRA continuation from a former employer, or retiree health benefits from a past employer do not qualify. Only active, current employment creates the protection.

Part A versus Part B: different rules

Most people qualify for premium-free Part A and there is little reason not to enroll at 65. Part A coverage does not affect your primary employer coverage for most services. The critical decision is Part B, which carries the monthly premium and the permanent late enrollment penalty if you miss your window. You can delay Part B penalty-free while covered by qualifying employer coverage. When that coverage ends, you have an 8-month Special Enrollment Period to enroll in Part B without penalty.

Still working at 65 and not sure what to do about Medicare?

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COBRA does not protect you

A common and costly mistake: leaving employment, electing COBRA continuation coverage, and assuming you are still protected from the Part B late enrollment penalty. COBRA is not qualifying coverage for this purpose. The 8-month Part B enrollment window begins when your active employment ends, not when COBRA ends. If you take COBRA for 18 months and then try to enroll in Part B, you have already missed your penalty-free window by ten months.

The retirement transition plan

When you plan to retire, coordinate your Medicare enrollment precisely. Notify Medicare of your upcoming retirement and set your Part B effective date to begin the month your employer coverage ends. Apply one to three months before your retirement date to ensure seamless coverage. If you are on an employer HSA plan, stop HSA contributions at least six months before Medicare begins to avoid the retroactive enrollment problem.

Frequently asked questions

How do I verify my employer's size for Medicare purposes?

Count the total number of employees during 50% or more of the calendar days in the previous year. Full-time, part-time, and temporary employees all count. If unsure, ask your HR department. The threshold is exactly 20, companies with 20 or more employees follow the employer-primary rule; companies with 19 or fewer follow the Medicare-primary rule.

What happens if I delay Part B and then my employer downsizes below 20 employees?

If your employer drops below 20 employees, Medicare becomes primary from that point forward. You would need to enroll in Medicare Part B promptly or risk a coverage gap. This is a scenario worth monitoring if you work for a smaller company approaching that threshold.

Can I have Medicare and keep my employer coverage simultaneously?

Yes. You can enroll in Medicare Parts A and B while also staying on your employer plan. The coordination rules determine which pays first. For larger employers, the employer plan pays first and Medicare supplements. This can reduce your out-of-pocket costs compared to either plan alone.

What about retiree health coverage from my former employer?

Retiree health coverage does not qualify as the basis for delaying Medicare. If you retire and receive retiree health benefits from your former employer, Medicare is primary and the retiree plan is secondary. You must enroll in Medicare Parts A and B at 65 or face penalties.

Bryce Casson

Licensed Independent Medicare Broker

Bryce Casson is an independent Medicare insurance broker who works with every major carrier. He does not represent any single insurer, which means his recommendations are based on what actually fits each client's situation, not on commissions or quotas.