Medicare late-enrollment penalties are generally added to your monthly premium. They are not usually one-time fees, and the Part B and Part D penalties can continue for as long as you have that coverage.

Penalties may not apply if you delayed enrollment because you had qualifying coverage or receive certain assistance.

Part A Late-Enrollment Penalty

Most people receive premium-free Part A and cannot be charged a Part A late penalty.

If you must buy Part A and do not enroll when first eligible, the monthly premium may increase by 10%. You generally pay the higher premium for twice the number of years you delayed.

Example: A two-year delay can mean a higher Part A premium for four years.

Part B Late-Enrollment Penalty

The Part B premium generally increases by 10% for each full 12-month period you could have had Part B but did not enroll.

Example: A two-full-year delay can create a 20% penalty. The penalty is based on the standard Part B premium and generally lasts as long as you have Part B.

You may avoid the penalty if you qualify for a Special Enrollment Period based on current-employment group coverage or another protected circumstance.

Part D Late-Enrollment Penalty

After your Initial Enrollment Period ends, a Part D penalty may apply if you go 63 consecutive days or more without Part D or other creditable drug coverage.

The monthly penalty uses the national base beneficiary premium, an amount Medicare sets for this calculation. Multiply 1% of that amount by the number of full months you had no Part D or creditable drug coverage. In 2026, the base premium used for this calculation is $38.99. The result is rounded to the nearest 10 cents and added to your Part D premium.

Because the national base premium can change yearly, the penalty amount can change too. It generally continues as long as you have Part D. People receiving Extra Help do not pay the penalty.

2026 calculation example: 12 full uncovered months × 1% × $38.99 = $4.6788, rounded to a $4.70 monthly penalty. Your coverage records determine how many full uncovered months count.

Going fewer than 63 days without drug coverage does not mean you can sign up whenever you want. You still need an applicable enrollment period.

What Coverage Protects You?

For Part B, coverage from your or your spouse's current employment may create a Special Enrollment Period. COBRA, retiree coverage, and Marketplace coverage do not necessarily provide the same protection.

For Part D, other drug insurance must be creditable, meaning it is expected to pay at least as much as standard Medicare drug coverage. The plan should send a creditable-coverage notice each year. Keep it as proof.

What If You Disagree With a Penalty?

For a Part D penalty, follow the instructions and deadline in your notice to ask for the decision to be reviewed. Include creditable-coverage notices, employer records and enrollment dates. For a Part B penalty, contact Social Security. Medicare’s penalty guide explains the current process and calculations.

Medicare policy sources last checked: October 8, 2026.