Medicare Enrollment Penalties

What does it cost to sign up for Medicare a year late? Not a late fee. A surcharge on your premium that follows you for the rest of your life. Medicare penalties don’t expire, and that single fact reshapes how you should think about the enrollment calendar.

The people who get caught aren’t careless. They’re often working past 65, or they assumed COBRA or a retiree plan had them covered. The rules don’t care about good intentions. They care about dates.

The Part B penalty, and why it’s permanent

Part B covers doctors and outpatient care, and it carries the penalty that does the most damage. For every full 12 months you were eligible and didn’t enroll without qualifying coverage, your premium rises 10%. Permanently.

Run the math. The 2026 standard Part B premium is $202.90 a month. Go three years late and you’re looking at a 30% surcharge, roughly $61 a month added on, every month, for as long as you’re on Medicare. Over a 25-year retirement that’s well over $18,000, and it climbs as the base premium rises. The penalty isn’t the sting. The permanence is.

The Part D penalty compounds quietly

Drug coverage has its own clock. The Part D penalty is 1% of the national base premium for each month you went without creditable drug coverage after you were eligible.

It looks small. A few months feels like nothing. But it’s permanent too, and it recalculates as the base premium drifts up, so a gap you barely noticed at 65 quietly grows for decades. The fix is almost free: keep creditable drug coverage, or enroll in a cheap Part D plan even if you take no medications, just to stop the clock.

The trap that catches working retirees

Here’s where careful people fall. If you’re 65 and still covered by a current employer’s group plan, and that employer has 20 or more employees, you can delay Part B without penalty. When you leave, a special enrollment period lets you sign up clean.

The danger is the coverage that looks like it should count but doesn’t:

• COBRA does not count. It is not coverage from a current employer, so it doesn’t protect you from the Part B penalty and doesn’t trigger a special enrollment period. People burn through 18 months of COBRA, then discover they were accruing penalties the whole time. The COBRA planning guide lays out the timing.
• Retiree health plans don’t count. Once you’re retired, that’s not current-employer coverage, even if it’s generous.
• A small employer doesn’t protect you. Under 20 employees, Medicare usually becomes primary at 65 whether you enrolled or not, which can leave you with gaps and penalties at once.

The other cost of waiting

The penalty is the obvious price. The hidden one is what waiting does to your Medigap rights. Your one-time Medigap open enrollment window opens when Part B starts and runs six months. Delay Part B and you delay that window, but you also risk colliding it with a new diagnosis, after which insurers in most states can underwrite or decline you. So a late enrollment can cost you the premium surcharge and the ability to buy supplemental coverage at a fair price. Two penalties wearing one coat.

How to stay clean

Enrollment penalties are almost entirely avoidable with attention to a few dates:

• Know your Initial Enrollment Period. It’s the seven-month band around your 65th birthday, three months before through three months after.
• If you’re working past 65, confirm your plan is creditable and that the employer is large enough to let you delay. Get it in writing from HR.
• When employer coverage ends, act inside your special enrollment period. It’s eight months for Part B, but waiting past it reopens the penalty risk.
• Never rely on COBRA to bridge to Medicare without checking the calendar first. The full timing sits in the Medicare enrollment timeline.

Most financial penalties give you a chance to recover. This one doesn’t. It prices a missed date into every premium for the rest of your life, which is exactly why a calendar reminder is the cheapest insurance you’ll ever buy.