Medicare Part B Late Enrollment Penalty Explained

Miss your Medicare Part B deadline and you can be hit with a permanent monthly penalty — one that follows you for the rest of your life. The Part B late enrollment penalty is one of the most punitive features of Medicare, and many of the people who get hit by it didn’t even realize they were supposed to enroll. Here’s how the penalty works, who’s actually exposed to it, and the situations where most people are protected.

The Medicare Part B late penalty: 10% added to your premium for each full 12 months you delayed, for life; employer coverage exempts you but COBRA and retiree plans do not

How the penalty is calculated

If you don’t enroll in Part B when you’re first eligible, and you don’t qualify for a Special Enrollment Period, your monthly Part B premium goes up by 10% for every full 12-month period you delayed. The penalty is permanent — once it’s applied, it stays added to your premium for the rest of your life.

Examples (using the 2026 standard Part B premium of $202.90/month):

1 year late: 10% penalty — $202.90 + $20.29 = $223.19/month, forever
2 years late: 20% penalty — $202.90 + $40.58 = $243.48/month, forever
5 years late: 50% penalty — $202.90 + $101.45 = $304.35/month, forever
10 years late: 100% penalty — double the standard premium, forever

The penalty applies to the standard premium amount each year, so as Part B premiums increase, your penalty dollar amount goes up too. Over a 20-year retirement, even a 1-year-late penalty can cost over $4,400 in extra premiums.

Who actually faces the Part B penalty

This is the most important point: most people don’t face the Part B penalty, because most people enroll on time or qualify for a Special Enrollment Period. The penalty primarily affects people who:

Don’t have any other creditable health coverage after age 65 and simply delay Medicare hoping nothing happens
Have COBRA or retiree health coverage after age 65 and incorrectly assume it lets them delay Part B
Have ACA marketplace coverage at 65 and don’t realize Marketplace plans don’t qualify for delaying Medicare
Live abroad or are out of the country when they turn 65 and miss the enrollment window
Mistakenly think Part A enrollment is enough and skip Part B

When you can safely delay Part B

You can delay Part B without penalty if you have creditable employer-based health insurance. The rules are specific:

You (or your spouse) must be actively employed — retiree coverage doesn’t count
The employer must have 20 or more employees — if 19 or fewer, Medicare becomes primary at 65 and you must enroll
The plan must provide active-employee coverage — not COBRA, not severance benefits, not retiree-only coverage

If you meet all three conditions, you can delay Part B for as long as you have qualifying employer coverage. When that coverage ends, you have 8 months to enroll without penalty — called the Special Enrollment Period.

Coverage that does NOT exempt you from the penalty

Many types of coverage seem like they should let you skip Part B, but they don’t. The most common pitfalls:

COBRA

COBRA coverage from a former employer does NOT count for delaying Medicare. People who retire at 64 and use 18 months of COBRA into age 65 often think their COBRA satisfies Medicare requirements. It doesn’t. The Special Enrollment Period clock starts when active employment ends, not when COBRA ends.

This is one of the most common penalty traps. If you’re on COBRA after 65, you should also enroll in Medicare Part B even though it means paying for both.

Retiree health coverage

If you retired before 65 and have retiree health insurance from your former employer, this does NOT exempt you from Part B enrollment. Retiree coverage is treated as secondary to Medicare and assumes you’re enrolled. Some retiree plans require Medicare enrollment as a condition of continued coverage — check your plan documents.

ACA Marketplace coverage

Health insurance from healthcare.gov or a state exchange does NOT count as creditable coverage for Medicare. If you reach 65 with Marketplace coverage and don’t enroll in Medicare, you face the Part B penalty. You should also know that your Marketplace premium subsidies end at 65 since you become Medicare-eligible — you usually pay the full unsubsidized premium even if you keep the plan.

VA, TRICARE, and Indian Health Service

VA benefits and Indian Health Service do NOT exempt you from Part B. TRICARE generally requires Part B enrollment as a condition of continued coverage. Don’t assume military or veterans coverage covers you for Medicare requirements.

Special Enrollment Periods (SEPs)

If you have qualifying employer coverage and lose it after 65, you have an 8-month Special Enrollment Period to enroll in Part B without penalty. The clock starts the month after either:

Your employment ends, or
Your employer-based coverage ends

Whichever happens first. So if you retire on May 31 with coverage continuing through June 30, your 8-month SEP starts June 1 (or July 1, depending on the situation) and runs through January or February.

Critical: Your SEP doesn’t restart if you go from active coverage to COBRA. The 8 months runs from when your active employer coverage ends.

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Other Medicare penalties to know about

Part D late enrollment penalty

If you don’t enroll in a Medicare prescription drug plan when first eligible and don’t have other creditable drug coverage, you owe a Part D penalty too. The math is different: 1% of the “national base beneficiary premium” (~$36 for 2026) per month delayed, added permanently to your Part D premium. So one year late = 12% penalty = ~$4.32/month extra, forever.

The Part D penalty is smaller than the Part B penalty in dollar terms but follows the same lifetime principle. Creditable coverage for Part D includes most employer drug plans, retiree drug plans, and the VA — check the annual notice of creditable coverage your employer or insurer must send you.

Part A penalty

Most people don’t pay for Part A — it’s premium-free for anyone with 40+ quarters of work history (or a spouse’s). For the small number of people who must pay for Part A and delay, the penalty is 10% added to the Part A premium for twice the number of years they delayed (not lifetime). This is uncommon.

How to fix it if you missed enrollment

If you missed your initial enrollment window and have no qualifying employer coverage, you generally must wait for the next General Enrollment Period (January 1–March 31 each year), with coverage starting the month after enrollment. The penalty applies once your coverage starts.

There are limited equitable relief paths if you can prove you were misinformed by an official source — for example, a Social Security office gave you incorrect advice. Documentation is key. The relief process is slow and not guaranteed, but worth pursuing if it applies.

Common mistakes

Assuming COBRA means you don’t need Part B. It doesn’t. The 8-month SEP runs from when active employment ends, not when COBRA ends.
Thinking Marketplace coverage exempts you. It doesn’t. ACA plans aren’t creditable coverage for Medicare.
Forgetting that retiree coverage usually requires Medicare enrollment. Retiree plans typically pay secondary to Medicare and may drop you if you don’t enroll.
Skipping Part B because Part A is free. Part A alone leaves huge gaps and triggers the Part B penalty if you go without creditable coverage.
Not enrolling within 3 months before turning 65. Late enrollment, even by one month past your 65th birthday, can delay coverage start by months.
Assuming small employer coverage protects you. If the employer has fewer than 20 employees, Medicare is primary at 65 — you must enroll on time.
Letting employer coverage end without enrolling within 8 months. Once the SEP closes, you wait until the General Enrollment Period and pay the penalty.

How to confirm you’re protected

If you’re working past 65, take these steps:

Confirm your employer has 20+ employees (or your spouse’s employer if you’re on their plan)
Get written confirmation that your coverage is “creditable” for Medicare delay purposes — HR or the insurer can provide this
When you eventually retire or lose coverage, document the exact date your active employment ends
Enroll in Part B within 8 months of that date
Keep proof of your continuous creditable coverage in case Medicare questions your enrollment timing

Bottom line

The Part B late enrollment penalty is permanent and meaningful, but most people aren’t exposed to it because they enroll on time or qualify for a Special Enrollment Period through active employer coverage. The traps are mostly around COBRA, retiree coverage, ACA plans, and small-employer situations — types of coverage that feel like they should count but don’t.

If you’re approaching 65 and have any kind of non-employer coverage, or if you’re on COBRA, the safe move is to enroll in Part B during your initial enrollment window even if you have to pay for it on top of other coverage. Once the penalty is applied, you can’t undo it — and over a 20-year retirement, the lifetime cost can be significant.

🆓 Need help with Medicare timing?

Our partner Chapter Medicare offers free one-on-one help from licensed advisors. They can determine if you qualify for a Special Enrollment Period and help you avoid permanent penalties.

📞 Call 615-639-1937 | 🔗 askchapter.org/money

ALWAYS FREE. No obligation.

Disclosure: We may receive a referral from Chapter if you choose to use their service. Chapter is a licensed health insurance agency and is not affiliated with or endorsed by Medicare or any government agency.

Medicare Part B Late Enrollment Penalty Explained

How the penalty is calculated

Who actually faces the Part B penalty

When you can safely delay Part B