Medicare Part B Late Penalty Calculator

How the Calculator Works

Enter the number of months you were eligible for Part B but did not enroll, not counting months when you had qualifying group coverage from current employment. The calculator divides those months by 12 and drops any remainder to find the number of full 12-month periods.

It then multiplies the number of full periods by 10% and applies that percentage to the standard Part B premium. The result is added to your monthly premium for as long as you have Part B. Higher earners may also pay IRMAA, which is estimated separately with the IRMAA calculator.

Worked Example

Suppose you were eligible for Part B but went 30 months without it and without qualifying employer coverage. Thirty months contains two full 12-month periods, so your penalty is 20%.

Using the 2026 standard premium of $202.90, 20% equals $40.58. Your estimated monthly Part B premium would be $202.90 plus $40.58, or $243.48. Because the penalty is a percentage of the standard premium, the dollar amount rises when the premium rises.

Limitations

This tool gives an estimate, not a quote, based on 2026 figures. The 2027 Part B premium had not yet been announced when this page was updated. Social Security determines your actual penalty using your records. If you had employer coverage based on current work, you may qualify for a Special Enrollment Period and no penalty.

Check your enrollment timing with the Medicare enrollment window tool, and read more about Medicare planning.

Calculators provide estimates for education only, not quotes or official determinations. We do not offer every plan available in your area. Currently, we represent 14 organizations which offer 119 products in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. This is a proprietary website and is not associated, endorsed or authorized by the Social Security Administration, the Department of Health and Human Services or the Center for Medicare and Medicaid Services. This site contains decision-support content and information about Medicare, services related to Medicare and services for people with Medicare. If you would like to find more information about the Medicare program please visit the Official U.S. Government Site for People with Medicare located at www.medicare.gov.

FAQ

Frequently asked questions

How is the Medicare Part B late penalty calculated?

The Part B penalty is 10% of the standard Part B premium for each full 12-month period you could have had Part B but didn’t. Partial years do not count. For example, 30 months without coverage equals two full periods, or a 20% penalty. The penalty is added to your monthly premium.

How long does the Part B penalty last?

In most cases, the Part B late enrollment penalty lasts for as long as you have Part B, which for most people means the rest of their lives. Because it is a percentage of the standard premium, the dollar amount can increase as the standard Part B premium increases from year to year.

Can I avoid the Part B penalty if I have employer coverage?

Usually, if the coverage is from current employment. With an employer of 20 or more employees, the group plan is generally primary and you can usually delay Part B without penalty. You then have an eight-month Special Enrollment Period after employment or group coverage ends, whichever comes first.

Does COBRA or retiree coverage count to avoid the Part B penalty?

Generally, no. COBRA and retiree coverage are not based on current employment, so they usually do not qualify you for the Special Enrollment Period that avoids the Part B penalty. Many people are surprised by this. If you have COBRA or retiree coverage, talk with Kris about Part B timing before your window closes.

What is the Part B premium for 2027?

The 2027 standard Part B premium had not been announced when this page was updated. CMS publishes the new amount each fall. For 2026, the standard premium is $202.90 per month with a $283 deductible. This calculator uses the 2026 figure, so 2027 estimates may differ once the new premium is published.

When can I sign up for Part B if I missed my window?

You can sign up during the General Enrollment Period, January 1 to March 31 each year. Coverage starts the month after you sign up. You may owe a late enrollment penalty. If you recently lost employer coverage from current work, you may instead qualify for a Special Enrollment Period.

Is this calculator result an official penalty amount?

No. The result is an estimate, not a quote. Social Security calculates your official penalty using your enrollment and coverage records. The calculator uses the 2026 standard premium. If your result looks surprising, Kris can review your work and coverage history with you in a no-cost consultation.