Medicare Late Enrollment Penalty Calculator

How the Part B Penalty Works

Did you skip Part B when you were first eligible, without a reason that qualifies for a Special Enrollment Period? Then Medicare adds 10% of the standard premium for each full 12 months you could have had Part B. Partial years do not count, so waiting 23 months is one period and waiting 24 months is two.

For people who sign up in 2023 or later, federal rules (42 CFR 408.24) count the months from the end of your Initial Enrollment Period to the end of the month you sign up. Months covered by a job-based plan from current work are left out, if you sign up within 8 months after that job or coverage ends.

Medicare's own 2026 example matches the second row: 24 months without Part B is a 20% penalty, so $202.90 plus $40.58 is $243.48, which Medicare rounds to $243.50.

How the Part D Penalty Works

The Part D penalty is 1% of the national base beneficiary premium for each full month you went without Part D or other creditable drug coverage after your Initial Enrollment Period. It only applies to gaps of 63 days or more in a row. The result is rounded to the nearest 10 cents and added to your plan premium.

Medicare's 2026 example: 14 months is 14% of $38.99, which is $5.46, rounded to $5.50 a month. CMS announced the 2027 base premium of $41.33 on July 28, 2026, so every Part D penalty rises a little in January.

The Part A Penalty

Most people get Part A free, so they never face this penalty. If you have to buy Part A and sign up late, your premium goes up 10%. You pay it for twice the number of years you waited. In 2026, the Part A premium is $565 a month with fewer than 30 work quarters, or $311 with 30 to 39. So the penalty is $56.50 or $31.10 a month.

How to Avoid or Remove a Penalty

• Job-based coverage. Are you or your spouse still working and covered by that job's plan? Then you can usually delay Part B. Sign up within 8 months after the job or coverage ends, and there is no penalty.
• Creditable drug coverage. Keep the yearly notice from your employer or plan that says your drug coverage is creditable. It is your proof against a Part D penalty.
• Extra Help. People who get Extra Help with drug costs do not pay the Part D penalty.
• Medicare Savings Programs. Medicare.gov says you will not pay a Part B penalty if you enroll in a Medicare Savings Program.
• Ask for a review. For Part D, you can ask for a reconsideration within 60 days of the date on the penalty letter. An independent reviewer decides, and you keep paying while you wait. For Part B, contact Social Security.

What About 2027?

The 2027 Part D base premium is final at $41.33, and this calculator already uses it. CMS usually announces the next year's Part B premium in November. As of November 7, 2026, the 2027 Part B premium has not been announced. We will add it as soon as CMS publishes it.

Related

Billing Medicare patients? See our Medicare billing guide and Medicare fee lookup. Patients can work out their share of a bill with our patient responsibility calculator.

Sources: Medicare.gov, Avoid late enrollment penalties (2026 examples); 42 CFR 408.22 and 408.24; CMS fact sheet, 2026 Medicare Parts A and B Premiums and Deductibles (November 14, 2025); CMS fact sheet, Medicare Part D 2027 National Average Monthly Bid Amount Information (July 28, 2026); CMS Part D late enrollment penalty reconsideration process. This calculator is an estimate; your penalty letter from Medicare or your plan is final.

Frequently Asked Questions