The mistake that costs the most
Only coverage from current employment — yours or a working spouse's — lets you delay Part B without penalty. COBRA is by definition coverage after employment ended. So is retiree coverage. So is a marketplace plan. None of them qualifies.
This catches people constantly, because it is genuinely counterintuitive: you have insurance, it came from an employer, and it still does not count.
How the two interact
If you become entitled to Medicare while already on COBRA
Your COBRA coverage can end. Becoming entitled to Medicare after electing COBRA is a permitted reason for the plan to terminate it — so do not assume COBRA will simply continue alongside.
If you become entitled to Medicare first, then leave the job
You are still eligible for COBRA, and your spouse and dependents may get a longer period — up to 36 months measured from your Medicare entitlement, rather than the usual 18. This is one of the more useful and least known provisions.
If you worked past 65 and took COBRA afterward
This is the version that catches the most people, and it is worth reading twice. If you stayed on your employer's plan past 65 because you were still working, you have a Special Enrollment Period for Part B — but it starts when the employment or the active coverage ends, whichever comes first. It does not start when COBRA ends, and electing COBRA does not pause it. You get eight months from that date. Spend eighteen months on COBRA first and the window has closed with ten months to spare, and you are waiting for the General Enrollment Period plus a lifetime penalty.
Which pays first
Once you have both, Medicare is generally the primary payer and COBRA is secondary. That is the reverse of active employment coverage, where the group plan pays first. Providers get this wrong often enough that it is worth stating when you present your cards.
What to do, and when
- Put your Initial Enrollment Period in your calendar — the three months before your 65th birthday month, that month, and the three months after. Seven months, and it does not move.
- Enroll in Part B during it unless you have coverage from current employment. COBRA is not that.
- Tell the COBRA administrator when you become Medicare-entitled. Do not let it be discovered later.
- Check what happens to your dependents — their period may be longer than yours.
- Stop HSA contributions before Medicare begins. More on that here.
- Check your COBRA drug coverage separately. Part D works differently from Part B: COBRA drug coverage can count as creditable and protect you from the Part D penalty, even though the same plan does nothing for Part B. Your plan must tell you each year whether its drug coverage is creditable — keep that letter.
Common questions
Does COBRA count as coverage for delaying Medicare Part B?
No, and this is the single most expensive misunderstanding in this area. Only coverage from current employment lets you delay Part B without penalty. COBRA, retiree coverage and marketplace plans do not qualify.
What is the Part B late-enrollment penalty?
10% of the Part B premium for each full 12-month period you could have had Part B and did not. It is added to your premium permanently — not for a year, for life.
Can I keep COBRA after I turn 65?
Sometimes, but becoming entitled to Medicare after electing COBRA is a permitted reason for the plan to end your COBRA. Do not plan on it continuing without confirming with the administrator.
Which pays first, Medicare or COBRA?
Medicare is generally primary and COBRA secondary. That is the opposite of active employment coverage, where the group plan pays first.
Can my spouse stay on COBRA if I go on Medicare?
Often yes, and potentially for longer than you would have had. Where the employee becomes Medicare-entitled, dependents may get up to 36 months measured from that entitlement rather than the usual 18.
When exactly is my Initial Enrollment Period?
Seven months: the three months before your 65th birthday month, the birthday month itself, and the three months after. Missing it is what creates the penalty.
I am on COBRA and just turned 65 — what should I do first?
Check whether you are inside your Initial Enrollment Period, and if so enroll in Part B now. If you have already missed it, a General Enrollment Period runs January 1 to March 31, though a penalty may apply.
I worked past 65 and then went on COBRA. How long do I have?
Eight months from the date the employment or the active employer coverage ended, whichever came first — not from the date COBRA ends. Electing COBRA does not pause that clock, which is why people on 18 months of COBRA routinely discover the window shut long ago.
Does COBRA protect me from the Part D drug penalty too?
Possibly, and this is where Part B and Part D genuinely differ. COBRA drug coverage can be creditable for Part D even though COBRA never counts for Part B. Your plan is required to tell you each year whether its drug coverage is creditable — keep that notice.
Is there someone who can walk me through this?
Yes, and this is a good one to talk through rather than read about, because the answer depends on your exact dates. Calling (866) 821-1808 connects you with a licensed agency.
Talk it through with a licensed agent
Which option is right depends on your state, your income and which doctors you need to keep. A licensed agent can walk through it with you in about eight minutes.
Free to call, no obligation, and we never ask you for payment. CobraScout is paid by the agency that answers, not by you. TTY 711.
Sources
- Medicare.gov, When to sign up for Part A and Part B
- Social Security Administration, Medicare enrollment and the Part B late-enrollment penalty
- U.S. Department of Labor, FAQs on COBRA Continuation Health Coverage for Workers
- HealthCare.gov, COBRA coverage and the Marketplace