COBRA is not creditable coverage for Medicare Part B, but it can be creditable for Medicare Part D if the plan’s prescription drug benefits are at least as generous as a standard Part D plan. That split is where most people get burned: staying on COBRA past your Medicare eligibility date will trigger a lifetime Part B late enrollment penalty, even though the same coverage may protect you from a Part D penalty. The standard Part B premium is $202.90 per month in 2026, and the penalty compounds on top of that for every year you delayed.1Centers for Medicare & Medicaid Services. 2026 Medicare Parts A & B Premiums and Deductibles2Centers for Medicare & Medicaid Services. Creditable Coverage
Why COBRA Does Not Count for Part B
Medicare lets you delay Part B without penalty only if you have coverage through active employment, meaning you or your spouse is still working and covered by the employer’s group health plan. COBRA is continuation coverage after employment has ended, not coverage based on current work, so it doesn’t qualify.3Medicare.gov. When Does Medicare Coverage Start
This catches people off guard because COBRA is literally the same plan you had while working. The card looks the same. The network is the same. But Medicare draws a hard line at active employment, and COBRA sits on the wrong side of it.4Medicare.gov. COBRA Coverage
The 8-Month Window COBRA Will Not Extend
When you stop working or lose employer group coverage (whichever comes first), you get a Special Enrollment Period of 8 months to sign up for Part B without penalty.5Social Security Administration. Sign Up for Part B Only Electing COBRA does nothing to that clock. It doesn’t pause, reset, or extend it.3Medicare.gov. When Does Medicare Coverage Start
Miss the window and you’re pushed to the General Enrollment Period, January 1 through March 31, with coverage starting the month after you sign up. That can leave a real gap in coverage, and the permanent penalty starts running.6Social Security Administration. Plan for Medicare – When to Sign Up for Medicare
What the Part B Penalty Actually Costs
The Part B late enrollment penalty adds 10% to your monthly premium for each full 12-month period you could have been enrolled but weren’t. Two years of delay is a 20% surcharge, which in 2026 works out to an extra $40.58 per month on top of the $202.90 standard premium, or roughly $243.50 total. Three years of delay is a 30% penalty, adding about $60.87 per month.7Medicare.gov. Avoid Late Enrollment Penalties
It’s not a one-time fee. You pay it for as long as you have Part B, which for most people means the rest of your life. And because it’s a percentage of the standard premium, the dollar amount grows each year as premiums rise.7Medicare.gov. Avoid Late Enrollment Penalties
When COBRA Is Creditable for Part D
Part D works differently. A COBRA plan’s drug coverage counts as creditable if its expected payouts are at least as generous as a standard Medicare Part D plan. Your former employer or plan administrator is required to send you a notice each year, before October 15, telling you whether the plan’s drug coverage is creditable.2Centers for Medicare & Medicaid Services. Creditable Coverage
If you have that notice confirming creditable status, you can hold off on enrolling in a stand-alone Part D plan or a Medicare Advantage plan with drug coverage. When your creditable COBRA drug coverage ends, you get a Special Enrollment Period of two full months after the month coverage ends to sign up for Part D.8Medicare.gov. Special Enrollment Periods Don’t assume. If you never received the annual notice, call the plan administrator and get the answer in writing.
The Part D Penalty and the 63-Day Rule
If you go 63 or more consecutive days without creditable drug coverage after your initial Part D enrollment period, you’ll owe a late enrollment penalty when you eventually sign up.2Centers for Medicare & Medicaid Services. Creditable Coverage The penalty is 1% of the national base beneficiary premium for every month you lacked coverage. In 2026 that base premium is $38.99, so each uncovered month adds about $0.39 to your monthly Part D bill.7Medicare.gov. Avoid Late Enrollment Penalties
Small numbers, but they add up over a long gap and last as long as you have drug coverage. A 14-month gap produces a 14% penalty, or about $5.50 a month in 2026, and it recalculates each year as the base premium changes.7Medicare.gov. Avoid Late Enrollment Penalties
What Happens to Your COBRA Once Medicare Starts
Becoming entitled to Medicare after electing COBRA is one of the grounds on which your employer’s plan is allowed to terminate your COBRA coverage early.9U.S. Department of Labor. FAQs on COBRA Continuation Health Coverage for Workers Not every plan drops you immediately, but you should plan for the possibility.
Spouses and dependents are treated separately. If the covered employee’s Medicare enrollment is what caused a spouse or dependent to lose the employer plan, that enrollment is its own qualifying event, and the spouse and dependents can receive up to 36 months of COBRA measured from the date the employee became entitled to Medicare.9U.S. Department of Labor. FAQs on COBRA Continuation Health Coverage for Workers That matters for a younger spouse who isn’t yet 65.
If You End Up With Both COBRA and Medicare
When you hold both, Medicare pays first and COBRA is secondary, picking up some costs Medicare doesn’t cover, such as remaining deductibles, copayments, or services outside Medicare’s scope.10Centers for Medicare & Medicaid Services. Medicare Secondary Payer Overview Medicare.gov warns that when COBRA is secondary, it may only pay a small portion of your medical costs and you may have to pay most costs yourself.11Medicare.gov. Who Pays First
You’re still paying the full unsubsidized COBRA premium (up to 102% of the plan’s cost) for that secondary role.12Legal Information Institute (LII). Consolidated Omnibus Budget Reconciliation Act (COBRA) A Medigap policy or a Medicare Advantage plan often gives you better secondary coverage at a comparable or lower price. Run the numbers before you write another COBRA check.
A Word on HSA Contributions
If you’ve been contributing to a Health Savings Account, Medicare enrollment ends that. You cannot contribute to an HSA once you’re enrolled in any part of Medicare, including Part A.13Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans If you’re already receiving Social Security when you turn 65, you’re automatically enrolled in Part A, so contribution eligibility ends whether you meant it to or not.6Social Security Administration. Plan for Medicare – When to Sign Up for Medicare
In the transition year, your contribution limit is prorated: divide the annual limit by 12 and multiply by the number of months before Medicare enrollment.13Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans The 2026 full-year limits are $4,400 for self-only coverage and $8,750 for family coverage, with an additional $1,000 catch-up at age 55 or older.14Internal Revenue Service. IRS Notice 2026-05 – HSA Contribution Limits Contributions made during any period of retroactive Medicare coverage count as excess and may trigger tax penalties. Existing HSA funds are still yours to spend on medical expenses, Medicare premiums, and even COBRA premiums; the restriction is on new contributions only.
The Bottom Line
Sign up for Part B during your 8-month Special Enrollment Period even if you’re electing COBRA. COBRA will not shield you from the Part B penalty, and that penalty lasts a lifetime. For Part D, confirm in writing that your COBRA drug coverage is creditable; if it is, you can wait, and use the two-month Special Enrollment Period after COBRA ends to pick up a Part D plan without penalty. If you already have both, look hard at whether COBRA’s secondary coverage is worth the full premium, and stop HSA contributions the month Medicare begins.