Medicare Part D Late Enrollment Penalty Calculator
Enter the months you went without creditable drug coverage after becoming eligible. The penalty is 1% of the national base premium ($38.99 in 2026) per month, rounded to the nearest dime, for as long as you have drug coverage.
Your numbers
Counted after your Initial Enrollment Period ended, once a gap reaches 63 days.
The base premium rose from $36.78 (2025) to $38.99 (2026); the penalty rises with it.
What uncovered months cost
1% × $38.99 × months, rounded to the nearest $0.10.
| Uncovered months | Rate | Per month | Per year | 20 years |
|---|---|---|---|---|
| 7 | 7% | $2.70 | $32 | $648 |
| 14 | 14% | $5.50 | $66 | $1,320 |
| 19 | 19% | $7.40 | $89 | $1,776 |
| 30 | 30% | $11.70 | $140 | $2,808 |
Small numbers, but they compound with premium growth and never stop. The bigger risk is the coverage gap itself.
How the math works
Medicare multiplies 1% by the number of full uncovered months and applies it to the national base beneficiary premium for the current year, rounding to the nearest ten cents. The result is added to whatever plan premium you pay. Because the base premium is reset each year, so is the penalty. The clock starts when a gap in creditable coverage reaches 63 consecutive days after your Initial Enrollment Period ends; a current employer plan with creditable drug coverage stops the clock, and so does any Part D or Medicare Advantage drug plan.
Sources
This tool is educational and simplifies by design. It computes published Medicare rules for the inputs you enter; it does not know your full situation, is not insurance, tax, or legal advice, and does not recommend any action. Nothing you type is transmitted or stored — the math runs in your browser. Confirm your dates and amounts with Social Security (1-800-772-1213), Medicare (1-800-MEDICARE), or a licensed professional before acting.
Part D penalty questions, answered
How long can I go without drug coverage before the penalty starts?
63 days. After your Initial Enrollment Period ends, any stretch of 63 or more days in a row without Part D or other creditable drug coverage starts counting uncovered months.
What is “creditable” coverage?
Drug coverage expected to pay at least as much as standard Part D. Most large employer plans, TRICARE, VA, and FEHB coverage qualify. Your plan must send you a creditable-coverage notice each year; keep it.
I don’t take any prescriptions. Can I skip Part D?
You can, but the penalty still accrues. Many people with no prescriptions enroll in the lowest-premium plan in their county to stop the clock, then switch during open enrollment if they need real coverage.
Does the penalty apply if I get drug coverage through a Medicare Advantage plan?
Yes, the same rule applies; the penalty is added to the plan’s premium.
Related tools and guides
Part B penalty calculator
The bigger penalty: 10% per year on the $202.90 premium, for life.
Open the tool →Enrollment window calculator
Find your windows from your birth date and your coverage end date.
Open the tool →
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