Working past 65

The COBRA trap

COBRA does not count as active employer coverage for Medicare. It doesn’t give you a Part B Special Enrollment Period and isn’t a reason to delay enrolling. Your eight-month Part B window starts when active employment ends — not when COBRA ends — so the safe move is to enroll in Part B when you stop working, even if you also take COBRA.

Reviewed by Scott Stafford, Licensed Insurance Agent

Last updated

The COBRA trap

One of the costliest Medicare mistakes is treating COBRA like a continuation of active employer coverage. It isn’t. COBRA does not open a Special Enrollment Period for Part B, and it is not a valid reason to delay enrolling. People who retire, elect COBRA, and assume they can wait often discover their Part B window has already closed.

Why COBRA isn’t enough

Your eight-month Part B Special Enrollment Period starts the month after your active employment — or the group plan based on it — ends, not when COBRA runs out. If you ride COBRA for several months and then try to enroll, the clock may already have expired, leaving you to wait for the General Enrollment Period for coverage and to pay a permanent late penalty on top of it.

Medicare pays first once you’re eligible

There’s a second problem. If you’re eligible for Medicare and on COBRA, Medicare is your primary coverage and COBRA pays second. That means relying on COBRA alone leaves you badly underinsured: COBRA assumes Medicare is paying the larger share whether or not you actually enrolled, so claims can come back largely unpaid.

What to do instead

Enroll in Part B when your active employment ends, even if you also elect COBRA to keep dental and vision or to cover a family member. Don’t wait for COBRA to end first. And if you’ve already fallen into this trap, ask Social Security about equitable relief — there’s a time-limited process that can sometimes waive the penalty and let you enroll.

The rule in one line: enroll in Part B when active work ends, not when COBRA ends.

Common questions

The COBRA trap FAQ

Does COBRA count as creditable coverage for Medicare?
No. COBRA is not considered active employer coverage for Part B, so it doesn’t give you a Special Enrollment Period or let you delay enrollment without a penalty.
If I have COBRA, does Medicare pay first?
Yes. Once you’re Medicare-eligible, Medicare is primary and COBRA is secondary — which is why relying on COBRA alone leaves big gaps if you skip Medicare.
When should I enroll in Part B if I’m offered COBRA?
When your active employment ends. That’s when your eight-month Part B window starts, and taking COBRA doesn’t pause that clock.

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