You're turning 65 with COBRA from your old job, and keeping COBRA instead of Medicare Part B sounds like the simple move. It usually isn't safe. COBRA, the Consolidated Omnibus Budget Reconciliation Act continuation coverage you buy after a job ends, doesn't count as coverage from a current job, so it won't let you put off Part B, and waiting for it to run out can leave you with a permanent penalty and a stretch of no coverage.
In This Guide
- Key Takeaways
- Can You Keep COBRA Instead of Medicare Part B?
- How the Part B Special Enrollment Period Really Works
- Why Waiting Out COBRA Instead of Medicare Part B Backfires
- Who Pays First Once You Have Both
- Frequently Asked Questions
- Learn More
Can You Keep COBRA Instead of Medicare Part B?
The short answer is no, not without taking on real risk. It's one of the most common mistakes people make with COBRA at 65, and it's an expensive one.
Here's why. The rule that lets you safely delay Part B is meant for people who keep working past 65 and stay on health coverage tied to that active job (yours or a spouse's). COBRA isn't that. It's continuation coverage you buy after the job ends, so Medicare doesn't treat it as coverage from a current employer. Because of that, COBRA does not let you put off Part B without exposing yourself to a late-enrollment penalty.Centers for Medicare & Medicaid Services. (n.d.). COBRA coverage. medicare.gov. Retrieved Jul 17, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65/cobra-coverage
So if you're 65 or older and COBRA is your only coverage, you generally need to get on Part B on Medicare's timeline, not COBRA's. Keeping COBRA is fine as extra coverage. Treating it as a reason to skip Part B is where people get burned.
One thing that's usually not the problem: Part A. Most people qualify for premium-free Part A because they have enough work history, so signing up for it at 65 costs nothing and there's little reason to wait.Centers for Medicare & Medicaid Services. (2026). 2026 Medicare Parts A & B Premiums and Deductibles. cms.gov. Retrieved Jul 23, 2026, from https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles The decision that actually carries a penalty is Part B, the part with the monthly premium.
How the Part B Special Enrollment Period Really Works
If you delay Part B because you had job-based coverage, Medicare gives you a Special Enrollment Period (SEP) to sign up later without a penalty. The trap is when that window opens and closes.
Your Part B Special Enrollment Period runs up to 8 months, and it starts when your job ends or your employer's group health plan ends, whichever comes first. It does not restart or extend when COBRA ends.Centers for Medicare & Medicaid Services. (n.d.). COBRA coverage. medicare.gov. Retrieved Jul 17, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65/cobra-coverage As Medicare's own COBRA page puts it, you have up to 8 months after you stop working, or lose that health insurance, to sign up for Part B without a penalty, whether or not you take COBRA.
The calendar is the whole trap. A lot of people assume the clock starts when their COBRA runs out, so they relax, use COBRA for a year or 18 months, and then go to enroll. By then the 8-month SEP tied to the old job is long gone. COBRA can last well past that window, which is exactly what makes this so easy to get wrong.
Why Waiting Out COBRA Instead of Medicare Part B Backfires
Miss the Special Enrollment Period and two things tend to happen at once, and neither is small.
First, the penalty. Signing up late for Part B triggers a late-enrollment penalty that gets added to your monthly Part B premium, and it sticks for as long as you have Part B.Centers for Medicare & Medicaid Services. (n.d.). COBRA coverage. medicare.gov. Retrieved Jul 17, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65/cobra-coverage That's the standard $202.90 premium in 2026 plus an extra amount on top, month after month, for the rest of your time on Medicare.Centers for Medicare & Medicaid Services. (2026). 2026 Medicare Parts A & B Premiums and Deductibles. cms.gov. Retrieved Jul 23, 2026, from https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles It's not a one-time fee you can shrug off.
Second, the gap. If you miss the SEP, you often can't enroll right away. You may have to wait for Medicare's General Enrollment Period and a later start date, which can leave you weeks or months with no Part B at all. During that gap, the outpatient care Part B normally covers, doctor visits, tests, and the like, is on you.
So the "save money by staying on COBRA" plan can flip into paying a higher premium for years and going uncovered in between. If you want to understand the broader penalty rules, see our guide to Medicare's late-enrollment penalties and how the main enrollment periods fit together.
Who Pays First Once You Have Both
Say you do the right thing and enroll in Part B on time, but you also keep COBRA for a while. Which one pays your bills?
In most cases, once you're entitled to Medicare, Medicare pays first (primary) and COBRA pays second (secondary).Centers for Medicare & Medicaid Services. (n.d.). COBRA coverage. medicare.gov. Retrieved Jul 17, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65/cobra-coverage That's straight from Medicare's coordination-of-benefits rules, and it's another reason not to lean on COBRA as your main coverage: if you skipped Part B, the primary payer you're counting on isn't actually there, and COBRA as the secondary payer won't fill that hole.
There's one exception worth knowing. During the 30-month coordination period for End-Stage Renal Disease (ESRD), the group health or COBRA plan can pay first and Medicare second.Centers for Medicare & Medicaid Services. (n.d.). COBRA coverage. medicare.gov. Retrieved Jul 17, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65/cobra-coverage If that situation applies to you or a family member, it's worth confirming the order with your plan, because the rules there are different.
Frequently Asked Questions
Can I keep COBRA instead of signing up for Medicare Part B?
Not safely. COBRA isn't coverage from a current job, so it doesn't let you delay Part B without risking a late-enrollment penalty. If you're 65 or older and COBRA is your coverage, you generally still need to enroll in Part B on Medicare's schedule.
When does my 8-month Part B Special Enrollment Period start?
It starts when your job ends or your employer's group health plan ends, whichever happens first, not when COBRA ends. You have up to 8 months from that point to sign up for Part B without a penalty, whether or not you take COBRA.
Do I have to take Medicare Part A if I have COBRA?
Most people take Part A at 65 because they've earned premium-free Part A through their work history, so there's usually no cost and little reason to delay it. The part that carries a penalty for waiting is Part B, the one with the monthly premium.
If I have both Medicare and COBRA, which one pays first?
Once you're entitled to Medicare, it generally pays first and COBRA pays second. The main exception is the 30-month coordination period for End-Stage Renal Disease, when the group health or COBRA plan can pay first instead.
Learn More
Find personalized help deciding when to sign up for Medicare Part B while you have COBRA at brevy.com.
The information on Brevy.com is for educational purposes only and is not a substitute for professional legal, financial, or medical advice. Rules vary by state and program and change frequently. Always verify with the relevant agency or a qualified professional. Brevy is not a law firm, financial advisor, or healthcare provider.