Home › Government & Benefits › Medicare Part D Late-Enrollment Penalty Calculator
Medicare Part D Late-Enrollment Penalty Calculator
If you go 63 or more days without Medicare drug coverage (or other creditable coverage) after your Initial Enrollment Period, you'll likely owe a permanent monthly penalty added to your Part D premium.
Example: Someone who waited 14 months to enroll in Part D, with no other creditable coverage, pays an estimated $5.50/mo extra every month — for as long as they have Medicare drug coverage.
What can change the math
- The penalty is recalculated each year using that year's national base beneficiary premium, so the dollar amount can change annually even though the percentage locked in at enrollment stays the same.
- The penalty applies for as long as you have Medicare drug coverage — it doesn't expire, even if you switch plans.
- You don't owe a penalty if you had other creditable prescription drug coverage (such as employer coverage) during the gap — 'creditable' means it's expected to pay at least as much as standard Medicare drug coverage.
Related calculators
Frequently asked questions
What counts as 'creditable' prescription drug coverage?
Coverage — such as from an employer, union, or the VA — that's expected to pay, on average, at least as much as Medicare's standard Part D coverage. Plans are required to tell you each year whether your coverage is creditable.
How long does the Part D penalty last?
In most cases, for as long as you have Medicare drug coverage. It's added to your monthly premium permanently, even if you switch to a different Part D plan.
What is the national base beneficiary premium?
A figure Medicare sets each year, used only to calculate the late-enrollment penalty — it's not the same as any specific plan's premium. It's $38.99 for 2026.