Medicare Late Enrollment Penalty Calculator

Calculate your Medicare Part B and Part D late enrollment penalties for 2026 based on how many months you went without coverage.

Medicare Part B and Part D each have their own late enrollment penalty, calculated differently. Part B adds 10% of the standard premium for every full 12 months you were late. Part D adds 1% of a benchmark premium for every month you went without creditable drug coverage. Both are generally permanent.

Missing your Medicare enrollment window doesn't just mean a delay, it can mean a lasting increase to your monthly premium. Part B and Part D penalties work differently, so this page has two separate calculators. Enter how many months you went without coverage in each to see your estimated penalty.

Part 1 of 2 — Part B Penalty

Medicare Part B Late Enrollment Penalty

Part 2 of 2 — Part D Penalty

Medicare Part D Late Enrollment Penalty

Both penalties share a similar shape but different math. The Part B penalty adds 10% of the standard premium for every full 12-month period you were eligible but unenrolled, without qualifying coverage. Because that's based on the CURRENT standard premium rather than a fixed dollar figure from whenever the gap happened, the penalty tends to grow over time even though the percentage itself never changes. The Part D penalty works similarly but by the month instead of the year: 1% of a specific benchmark figure called the national base beneficiary premium, for every month you went without Part D or other qualifying drug coverage. That benchmark isn't the same as your actual plan's premium, it's a separate number used only for this calculation, and like the Part B penalty, it's recalculated every year, so your dollar penalty can shift even though the underlying percentage stays the same. Neither penalty applies if you had valid alternative coverage during the gap, most commonly an active employer plan. If you're not sure whether that applied to your situation, the site's Medicare Enrollment Period Finder tool can help you check.

Frequently Asked Questions

How is the Medicare Part B late enrollment penalty calculated?

10% of the current standard Part B premium for each full 12-month period you were eligible but didn't enroll, without qualifying coverage like an active employer plan. In 2026, the standard premium is $202.90/month.

How is the Medicare Part D late enrollment penalty calculated?

1% of the national base beneficiary premium ($38.99 in 2026) for every full month you went without Part D or other creditable drug coverage, rounded to the nearest $0.10.

Do these penalties ever go away?

Generally no. Both penalties are permanent additions to your premium for as long as you have that part of Medicare, though the exact dollar amount can change yearly since it's based on a percentage of a figure that changes annually.

What counts as "creditable" prescription drug coverage for Part D?

Coverage, such as from a current employer plan, that's expected to pay at least as much as standard Medicare Part D coverage. If you had creditable coverage, you generally won't owe a Part D penalty even if you didn't have Part D itself.

I had employer coverage when I turned 65. Do I still owe a penalty?

Usually not, as long as that coverage qualified as creditable (for Part D) or was an active employer group health plan (for Part B). This tool assumes any gap wasn't covered by a valid Special Enrollment Period — check the site's Medicare Enrollment Period Finder if you're unsure.

Can I appeal a late enrollment penalty?

Yes. If you believe the penalty was calculated incorrectly, or you had valid creditable coverage that wasn't properly considered, you can file an appeal using instructions in the notice you receive.

This calculator provides a general estimate based on the official 2026 Medicare penalty formulas and does not constitute financial or legal advice. It assumes any coverage gap was not protected by a valid Special Enrollment Period; if you're unsure, your actual penalty determination is made by Medicare, not this tool. For your official penalty amount or to file an appeal, contact the Social Security Administration or your Part D plan directly.