Part D Late Enrollment Penalty Calculator (2026)

Your Medicare Part D late enrollment penalty is 1% of the national base beneficiary premium ($38.99 in 2026) for every full month you went without Part D or other creditable prescription drug coverage, rounded to the nearest $0.10 — and it is added to your drug plan premium permanently.

Worked example: 24 months without creditable coverage → $38.99 × 1% × 24 months = $9.40/month added permanently to your Part D premium.

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Last reviewed July 9, 2026 by Scott Martin, Licensed Medicare Advisor

When the penalty applies

Medicare assesses the penalty if you go 63 or more continuous days without Part D or other creditable drug coverage after your Initial Enrollment Period ends. Creditable coverage is drug coverage expected to pay at least as much as Medicare's standard Part D benefit — most employer and union plans, VA coverage, and TRICARE qualify. Your plan must tell you each year whether your coverage is creditable. See what counts as creditable coverage →

The penalty is permanent — but its growth is capped

Once assessed, the penalty stays on your premium for as long as you have Medicare drug coverage. Because it is recalculated against each year's national base beneficiary premium, the dollar amount can rise over time — though the Inflation Reduction Act caps the base premium's growth at 6% per year through 2029.

The cheapest fix is prevention: enroll in a Part D plan (or a Medicare Advantage plan with drug coverage) when you're first eligible, even a low-premium plan, if you don't have creditable coverage elsewhere. Read the full guide to the Part D penalty →

Frequently asked questions

How is the Part D late enrollment penalty calculated?

The penalty is 1% of the national base beneficiary premium ($38.99 in 2026) multiplied by the number of full months you went without Part D or other creditable prescription drug coverage, rounded to the nearest $0.10. Example: 24 months without coverage means $38.99 × 1% × 24 = $9.40 added to your Part D premium every month.

When does the Part D penalty apply?

The penalty applies if you go 63 or more continuous days without Part D or other creditable drug coverage (such as employer, union, VA, or TRICARE drug coverage) after your Initial Enrollment Period ends. Shorter gaps — for example while switching plans — do not trigger it.

Is the Part D late enrollment penalty permanent?

Yes, in general. Once assessed, the penalty is added to your Medicare drug plan premium for as long as you have Part D coverage. It is recalculated against each year’s national base beneficiary premium, so the dollar amount can change from year to year.

Is there a limit on how fast the penalty can grow?

The penalty itself has no cap — every additional month without creditable coverage adds another 1% of the base premium. But the Inflation Reduction Act caps growth of the national base beneficiary premium at 6% per year through 2029, which limits how quickly an existing penalty amount can rise. For 2026, the base premium rose the full 6% to $38.99.