The short answer
The Medicare Part B late enrollment penalty adds an extra 10 percent to your monthly premium for each full 12 month period you could have signed up but did not. For most people it lasts as long as they have Part B. A Special Enrollment Period or a Medicare Savings Program generally prevents it.
Say you go two years without signing up and without other coverage. The premium you are quoted afterwards is not the standard one, and it never will be again. The penalty is not a fee you clear. It is a change to the bill.
How is the Part B late enrollment penalty calculated?
The Part B late enrollment penalty is calculated as an extra 10 percent for each full 12 month period you could have signed up for Part B but did not. The count runs on time spent without coverage similar in value to Medicare, so the longer the unprotected gap, the higher the percentage.
Medicare.gov's own worked example shows the shape. Wait two full years with no qualifying coverage and no Special Enrollment Period and the penalty is 20 percent. It is added on top of the standard Part B monthly premium, with the total rounded to the nearest 10 cents.
The word full carries real weight in that formula. The percentage builds in whole 12 month steps, one for each complete year of the gap.
How much is the penalty?
How much the Part B penalty costs changes from year to year, by design. Call it the Moving Base: the percentage multiplies the standard Part B premium of the current year, and that premium can change annually, so the same missed years get repriced every year you stay enrolled.
The Moving Base is a reading of the government's own example, which applies the penalty percentage to that year's standard premium. Both mechanics, the fixed percentage and the moving premium, are Medicare.gov's. The naming is ours.
No dollar amount appears on this page on purpose. The premium the percentage lands on is a year-tagged figure that belongs to the pages that track it, and any number printed here would go stale. The percentage is the part that is durably true.
Income is a separate mechanic entirely: some people pay a higher Part B premium because of income, but the government's example computes the penalty from the standard premium, not from the income-adjusted one.
Part A has a penalty of its own, and it works differently enough to catch people who assume the two match.
Most people pay no Part A premium, because they or a spouse paid Medicare taxes long enough while working. If you do have to buy Part A and you do not buy it when first eligible, the monthly premium may go up 10 percent, and you pay that increase for twice the number of years you could have had Part A and did not.
So the Part B penalty runs for as long as you hold Part B, while the Part A penalty runs for a counted stretch and then stops.
How long do I have to pay it?
You pay the Part B penalty every month, for as long as you have Part B coverage. It rides inside the premium bill rather than arriving separately, and it is not a one-time late fee. For most people, Medicare.gov says plainly, that adds up to a lifetime penalty.
That phrasing is the government's own framing of its penalty family: added to your monthly premium, not a one-time late fee, usually charged for as long as you have that type of coverage.
One penalty in the family runs differently, and the contrast is worth one paragraph. Premium-Part A, for people who have to buy Part A, carries a penalty of 10 percent added to the premium, paid for twice the number of years you did not sign up, and then it ends.
How do I avoid the Part B penalty?
Avoiding the Part B penalty means never having an unprotected gap. Sign up during your 7 month Initial Enrollment Period, or hold other coverage similar in value to Medicare, like employer coverage, and use the Special Enrollment Period it earns you. Enrolling in a Medicare Savings Program also generally means no penalty.
The Initial Enrollment Period is the 7 months around your 65th birthday: the 3 months before, your birthday month, and the 3 months after.
A Special Enrollment Period is powerful and perishable. It exists only for certain situations, it is available for a limited time, and missing it means waiting for the next General Enrollment Period, possibly with the penalty attached.
A Medicare Savings Program is state-run help for people with limited income and resources toward premiums and other costs. Qualifying for one generally means the Part B penalty does not apply to you.
Does the penalty ever go away?
The Part B penalty has no built-in end date: it is usually charged for as long as you have Part B. The protections that exist prevent it rather than end it: a Special Enrollment Period or a Medicare Savings Program. One penalty does expire: Premium-Part A's, after twice the delayed years.
That asymmetry is the honest summary of the family. Part D's penalty, covered in its companion article, follows Part B's lifetime pattern rather than Part A's expiring one.
Two penalties exist and they end differently, which is why the answer depends on which one you have.
| Part B penalty | Part A penalty | |
|---|---|---|
| Who pays it | Anyone who took Part B late | Only people who buy Part A |
| How long it lasts | As long as you have Part B | Twice the years you delayed |
| Does it end | No | Yes, after that stretch |
The bottom row is the whole difference. One is a permanent addition and the other is a countable one.
So the leverage all sits before the penalty attaches, never after. Which is why the two questions that matter are the ones the next section and the next article answer: does a window protect you now, and which window applies.
Does employer coverage protect me from the penalty?
Employer coverage protects you from the Part B penalty while it is current coverage, through your job or your spouse's job, and for 8 months after the job or the coverage ends, whichever comes first. Two look-alikes protect nothing: COBRA and retiree coverage do not count.
Medicare.gov is explicit on both. COBRA is not considered group health plan coverage, and getting COBRA does not change when the 8 month window ends. And the list of situations that do not qualify for a Special Enrollment Period includes COBRA or retiree coverage ending, and missing your 8 month window after stopping work.
One narrower rule for readers with a disability: coverage through a family member's job, other than a spouse, counts only when that employer is in a large group health plan.
Working past 65 and leaving employer coverage safely have their own articles. What they share is a window that opens quietly and closes on a date nobody sends you.
What changed this year
The percentage is the rule and it is written into law rather than set each year. What moved is the figure it multiplies. The standard premium rose for 2026, so the identical penalty costs more this year than last without any rule changing at all.
The Part B late enrollment penalty is 10 percent of the standard premium for each full 12 months you could have had Part B and did not. The standard premium is 202.90 dollars a month in 2026, up 17.90 dollars from 185.00 dollars in 2025.
So the identical penalty is more expensive this year than last, without any rule changing. A penalty of 20 percent is 20 percent of a larger number.
The Part B deductible moved with it, to 283 dollars in 2026 from 257 dollars in 2025.
Source: the CMS fact sheets of November 14, 2025 and November 8, 2024.
What this means for you
The Part B penalty is arithmetic, not judgment: 10 percent per missed full year, on a base that moves, for as long as you hold Part B. Every protection is a window with a clock, so the whole subject reduces to knowing which window you are in before it closes.
If you are inside a window now, the window article beside this one shows the calendar. If the deadline already passed, the missed-enrollment article walks the repair paths in order.
FAQ
Is the Part B penalty a one-time fee?
No, and this is the single most expensive misunderstanding about it. Medicare.gov describes its late enrollment penalties in three strokes. They are added to your monthly premium. They are not a one-time late fee. And they are usually charged for as long as you have that type of coverage, which for most people means a lifetime penalty.
So a Part B penalty is best understood as a permanent rent increase on your coverage rather than a fine you pay once and clear.
That is also why prevention is worth so much more than repair here: every protection, from the Initial Enrollment Period to a Special Enrollment Period, exists before the penalty attaches, and nothing routine removes it afterward.
Is there a late penalty for Part A too?
Only for people who have to buy Part A. Most people qualify for premium-free Part A, and Medicare.gov ties the Part A penalty specifically to those who must pay a Part A premium, called Premium-Part A.
For them, buying late means the monthly premium may go up 10 percent, paid for twice the number of years they did not sign up, after which it ends.
That expiration makes Premium-Part A the exception in the penalty family: Part B and Part D penalties usually run for as long as the coverage does. If you are unsure which side of the premium-free line you are on, that question is answered on the eligibility side of this publication, not by guessing.
I had COBRA when my employer coverage ended. Am I protected?
No, and this is the trap Medicare.gov flags most directly. COBRA is not considered group health plan coverage, so it does not create the employer Special Enrollment Period, and starting COBRA does not change when that window ends.
The 8 month clock runs from when the employment or the group coverage ends, whichever comes first, regardless of the COBRA card in your wallet.
The government's list of situations that do not qualify for a Special Enrollment Period says it plainly: your COBRA coverage or retiree coverage ending does not qualify. Anyone leaving a job at or after 65 should treat the job's end date, not COBRA's end date, as the deadline that matters.
Does the penalty percentage keep growing after I sign up?
The percentage is built from your gap. It is an extra 10 percent for each full 12 month period you could have signed up but did not, and Medicare.gov describes penalties as based on how long you went without coverage similar to Medicare. Signing up is what ends the gap the formula measures.
What continues to move afterward is the dollar amount, because the percentage is applied to the standard Part B premium of the current year, and that premium can change annually. So the penalty share of your bill is set by your history, while the bill itself keeps tracking each year's premium. The history is fixed; the base is not.
Can a Medicare Savings Program spare me the penalty?
Generally yes. Medicare.gov states that you will not have to pay a Part B penalty if you qualify for a Special Enrollment Period or you enroll in a Medicare Savings Program. These programs are state-run help for people with limited income and resources, paying toward premiums and other Medicare costs.
For someone already facing a penalty scenario with a limited income, this is the single most valuable sentence on the page, because it is the one path that is about your present circumstances rather than your enrollment history. The programs themselves, their levels, and how to apply through your state are covered in the Savings section of this publication.
