United States · Medicare costs

Medicare late enrollment penalty calculator.

Estimate what signing up late adds to your Part B and Part D premiums, per month and over the years you will pay it.

Part B adds 10% of the standard premium ($202.90 in 2026) for each full 12 months you could have enrolled but did not. Part D adds 1% of the national base beneficiary premium ($38.99 in 2026) for each full month without creditable drug coverage, rounded to the nearest $0.10.

2026 amountsCMS and Medicare.govVerified October 2, 2026

Your inputs

Last day of your initial enrollment period (IEP)For most people the IEP is the 7 months around your 65th birthday and ends on the last day of the month after you turn 65.

Date you signed up for Part BOnly the month matters for Part B.

Months of Part B delay covered by a special enrollment periodExample: months you had employer coverage based on current work. These months do not count. Enter 0 if unsure.

Date your Part D drug coverage starts

Months with creditable drug coverage since your IEP endedMonths covered by a plan that your insurer told you was creditable (as good as Medicare's).

I went 63 days or more in a row without Medicare or creditable drug coverageUntick if no single gap reached 63 days. Then there is no Part D penalty.

I get Extra Help (Part D low-income subsidy)People with Extra Help do not pay a Part D penalty.

Standard Part B premium per month

National base beneficiary premium per month

Years you expect to pay the penalty

2026 estimate

How the penalty is figured

Part B. Under 42 CFR 408.22 your standard monthly premium is increased by 10% for each full 12 months of delay. Under 42 CFR 408.24, for people who first enroll on or after January 1, 2023, the months counted run from the close of your initial enrollment period to the close of the month in which you first enroll. Months covered by a special enrollment period are not counted, and part-years are dropped. Medicare.gov describes the result as lasting, for most people, as long as you have Part B.

Part D. Under 42 CFR 423.46 you owe a penalty if you go 63 or more days in a row after your IEP without Part D or other creditable drug coverage. Under 42 CFR 423.286(d)(3) it is 1% of the base beneficiary premium for each uncovered month. Medicare.gov states it is rounded to the nearest $0.10 and added to your plan premium, and that the base beneficiary premium is $38.99 in 2026. The base premium changes each year, so the dollar penalty changes with it.

Formulas: Part B penalty = standard premium × 10% × full 12-month periods. Part D penalty = 1% × base premium × uncovered full months, rounded to the nearest $0.10. Lifetime cost = monthly penalty × 12 × years.

Worked example

Your IEP ended January 31, 2023 and you signed up for Part B in February 2026. Counting February 2023 through February 2026 gives 37 months, which is 3 full 12-month periods, so 30%. 30% of $202.90 is $60.87 a month, or $730.44 a year. For Part D, 37 full months with no creditable coverage gives 1% × $38.99 × 37 = $14.43, rounded to $14.40 a month.

Limits of this estimate: it uses one 2026 premium for every future year, assumes you gave the dates and creditable months correctly, and does not model Extra Help eligibility, Medicare Savings Programs, Part A, income-related surcharges (IRMAA), or the Part D premium itself. Part D counts full months from the day after your IEP ends to the day your coverage starts.

Official sources: 42 CFR 408.22 and 42 CFR 408.24 (Part B); 42 CFR 423.46 and 42 CFR 423.286 (Part D); Medicare.gov Part D late enrollment penalty ($38.99 base premium, rounding); Medicare.gov avoiding penalties; CMS 2026 Parts A & B premiums fact sheet ($202.90). Amounts as of 2026; verified October 2, 2026.

Frequently asked questions

Does the Part B penalty ever go away?

For most people no. Medicare.gov says late enrollment penalties are usually charged for as long as you have that coverage. Because it is a percentage of the standard premium, the dollar amount rises when the premium does.

How can I avoid the Part B penalty?

Medicare.gov says you generally will not owe it if you qualify for a special enrollment period, for example when you delayed because of coverage from current work, or if you enroll in a Medicare Savings Program.

What counts as creditable drug coverage?

Coverage expected to pay on average at least as much as Medicare's standard drug coverage. Your plan must tell you each year whether it is creditable. Keep those notices.

Why 63 days?

42 CFR 423.46 ties the Part D penalty to a gap of 63 or more days in a row without Part D or creditable coverage. A shorter gap does not trigger it.

Is the penalty added to my IRMAA?

They are separate. The Part B penalty is a percentage of the standard premium, while IRMAA is an income surcharge. Both can apply to the same person.

Can I dispute a Part D penalty?

Under 42 CFR 423.46 you can ask for reconsideration with proof of creditable coverage. Ask your plan how to file.

Estimate only

This is an educational estimate, not Medicare, legal or benefits advice. Social Security and your Part D plan decide your actual penalty; confirm with Medicare at 1-800-MEDICARE.