Medicare late enrollment penalties: Part A, Part B and Part D

Medicare charges extra if you sign up late without a good reason. The extra is small each month, but for Part B and Part D it usually never goes away. Here is how each penalty works, with the examples Medicare itself uses.

Part B: 10% for every year you waited

You pay an extra 10% for each year you could have signed up for Part B but did not. Only full 12-month periods count, so 23 months late is one year's penalty and 24 months is two.

Medicare's example: you waited 2 full years and did not qualify for a Special Enrollment Period. Your penalty is 20%. In 2026 the standard premium is $202.90, 20% of that is $40.58, and after rounding to the nearest 10 cents you pay $243.50 a month.

You generally do not pay it if you qualify for a Special Enrollment Period, or if you enroll in a Medicare Savings Program.

Part D: 1% for every month

The drug-coverage penalty is counted in months. You pay an extra 1% for each month, which is 12% a year, if you did not join a Medicare drug plan when you first got Medicare, or if you went 63 days or more without creditable drug coverage. Creditable means coverage that is similar in value to Part D.

The percentage is not applied to your own plan's premium. It is applied to a national figure called the base beneficiary premium, which is $38.99 in 2026. Medicare's example: 14 months late is 14% of $38.99, or $5.46, rounded to $5.50 a month. That is added to whatever your plan charges.

The base premium changes every year, so the dollar amount of the penalty changes too. For 2027 it is $41.33.

You generally do not pay it if you have creditable drug coverage or you qualify for Extra Help.

Part A: rare, and it ends

Most people pay no premium for Part A, so most people never see this one. If you have to buy Part A and do not buy it when you are first eligible, your monthly premium may go up 10%. You pay the higher premium for twice the number of years you did not sign up. Two years late means four years of the higher premium.

How long they last

The Part B and Part D penalties are usually charged for as long as you have that type of coverage. For most people that is a lifetime penalty. Only the Part A penalty runs out.

Work out your own

The late enrollment penalty calculator does the arithmetic for any number of months, and the enrollment periods page shows when your first sign-up window opens and closes.