Picture a man in Lexington who retires at 66. He worked past 65, kept his employer health plan the whole time, and did everything right up to his last day. On his way out, HR hands him a packet and tells him he can keep his same insurance for 18 more months through COBRA. Same doctors, same coverage, same card in his wallet. He signs up, pays the premium every month, and figures he'll deal with Medicare when COBRA runs out.

Fourteen months later he calls to enroll in Medicare and finds out two things. First, he missed his enrollment window, which closed quietly months earlier. Second, he now owes a Part B late enrollment penalty that will be added to his premium every single month for the rest of his life.

He had an insurance card the entire time. He paid premiums the entire time. None of it counted.

This is the COBRA trap, and HR departments across South Carolina hand it to retirees every week without ever mentioning the deadline hiding inside the packet.

What COBRA actually is

COBRA is a federal law that lets you keep your employer's group health plan after you leave a job, usually for up to 18 months. You pay the full premium yourself, which often comes as a shock on its own, since the employer is no longer chipping in.

For someone under 65 who leaves a job, COBRA can be a reasonable bridge. The trap only springs on people who are 65 or older when their employment ends, because at that point Medicare's rules take over, and Medicare treats COBRA very differently than most people expect.

The rule nobody mentions

While you're actively working, employer coverage from a company with 20 or more employees counts as creditable coverage for Medicare Part B. That's why you can work past 65, delay Part B, and pay no penalty.

The moment you stop working, that protection ends. Medicare gives you a Special Enrollment Period of 8 months to sign up for Part B, and here's the part that catches people: the clock starts when your employment ends, not when your COBRA ends.

COBRA does not count as creditable coverage for Part B. It doesn't matter that it's the exact same plan you had the week before. It doesn't matter that you're paying more for it than you ever did as an employee. In Medicare's eyes, the day you stopped working is the day your countdown began.

So the retiree who takes 18 months of COBRA sails right past his 8-month window without ever hearing a warning. By the time COBRA runs out, his Special Enrollment Period is long gone.

What missing the window actually costs

Two things happen, and both hurt.

The penalty comes first. Medicare adds 10% to your Part B premium for every full 12-month period you could have had Part B and didn't. That penalty is permanent. With the standard Part B premium at $202.90 a month in 2026, a single year of delay adds roughly $20 a month, every month, for life. Wait two years and it's 20%. The premium the penalty is calculated on also goes up over time, so the dollar amount grows with it.

The gap comes second. Once your Special Enrollment Period closes, you can only sign up during the General Enrollment Period, which runs January 1 through March 31, with coverage starting the month after you enroll. Miss your window in the spring and you could spend the better part of a year waiting for the next chance to get covered.

The second trap hiding inside the first

There's one more layer, and it's the one that turns an expensive mistake into a devastating one. Once you're 65 and no longer actively employed, Medicare is supposed to be your primary insurance. COBRA pays secondary.

Some COBRA plans process claims as if Medicare already paid its share, whether you enrolled in Medicare or not. A retiree who skipped Part B can end up with a plan that only covers the small slice Medicare would have left over, leaving him responsible for the bulk of a hospital bill he thought was covered. People have discovered this after a surgery, not before.

Paying full COBRA premiums for coverage that pays secondary to a Medicare enrollment you don't have is the worst deal in health insurance, and nobody signs up for it on purpose.

The checklist before your last day of work

If you're 65 or older and retirement is on the horizon, run through this before you leave:

1. Mark the real deadline. Your 8-month Part B window starts the month after your employment ends. Put it on the calendar before you clean out your desk.
2. Enroll in Part B during that window, even if you take COBRA for dental or to bridge a spouse. Part B and COBRA can overlap, but Part B can't wait.
3. Get Form CMS-L564 from your employer before you lose easy access to HR. It proves you had employer coverage and keeps the penalty off your record.
4. Ask what COBRA actually covers once you're Medicare-eligible. Get the primary-versus-secondary answer in writing.
5. Think about your spouse. If a younger spouse is on your employer plan, their coverage needs its own plan. COBRA might make sense for them even while you move to Medicare.

Free advice beats a lifetime penalty

Every dollar of this penalty is avoidable with the right timing, and the right timing is easy when someone tells you the rules before your last day instead of after.

Jennifer handles Medicare for our clients across Lexington, Columbia, and the Midlands, and walking retirees through this exact transition is a big part of what she does. The consultation costs nothing, your premiums are the same whether you use an agent or not, and a 20-minute conversation before you retire can save you a penalty that never goes away.

Call or text Jennifer at 843-509-2462, or reach out through our contact page. If your retirement date is already set, sooner is better.

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FAQ

Does COBRA count as creditable coverage for Medicare Part B? No. Only coverage from active employment at a company with 20 or more employees lets you delay Part B without penalty. COBRA does not qualify, even though it's the same plan you had while working.

When does my Medicare Special Enrollment Period start if I take COBRA? The month after your employment ends. Taking COBRA does not pause or extend the 8-month window. Many people on COBRA miss their window without realizing it was running.

How much is the Part B late enrollment penalty? 10% of the Part B premium for every full 12-month period you delayed, added to your premium permanently. The penalty grows as the base premium rises each year.

Can I have COBRA and Medicare at the same time? Yes, in some situations, though Medicare pays primary once you're 65 and no longer actively working. If you became eligible for Medicare before electing COBRA, enrolling in Part B alongside COBRA protects you from both the penalty and unpaid claims.

What about COBRA and Part D drug coverage? COBRA drug coverage can count as creditable for Part D if the plan certifies it. That's a separate question from Part B, where COBRA never counts. Check both before deciding.

I already missed my window. What now? Enroll during the General Enrollment Period, January 1 through March 31, with coverage starting the month after you sign up. Talk to an agent about bridging the gap and confirming exactly what penalty applies, since the math depends on your specific dates.