Part D Late Enrollment Penalty Calculator
Updated August 2, 2026
If you go without creditable prescription drug coverage after you're first eligible for Medicare, you'll owe a permanent Part D late enrollment penalty. It's 1% of the national base beneficiary premium ($38.99 in 2026) for every full month you were eligible but uncovered — added to your Part D premium for as long as you have Part D. Enter how many months you went without coverage to see what it costs.
Your monthly penalty
$9.40/mo
24 full uncovered months = 24% of the $38.99 base premium, rounded to the nearest 10 cents.
That's an extra $112.80/year, added to your Part D premium for as long as you have Part D — and it's recalculated upward as the base premium rises.
Counts only full months you were eligible for Part D and had no creditable drug coverage. Uses the 2026 base premium of $38.99; Medicare recalculates the penalty each year against the then-current base. Educational estimate, not advice.
How the penalty is calculated
Medicare takes 1% of the national base beneficiary premium for each full month you were eligible for Part D but went without creditable coverage, then rounds the monthly amount to the nearest 10 cents. In 2026 the base premium is $38.99, so:
penalty/month = (uncovered months × 1%) × $38.99
A 24-month gap is 24% × $38.99 = $9.36, which rounds to $9.40 per month — about $112.80 a year, every year, on top of whatever your plan charges. Because the penalty is a percentage of a base amount that rises most years, it isn't frozen: the same gap costs a little more each year.
What a delay costs over time (2026 base premium)
| Months uncovered | Penalty rate | Per month | Per year |
|---|---|---|---|
| 7 months | 7% | $2.70 | $32.40 |
| 12 months (1 yr) | 12% | $4.70 | $56.40 |
| 24 months (2 yr) | 24% | $9.40 | $112.80 |
| 36 months (3 yr) | 36% | $14.00 | $168.00 |
| 48 months (4 yr) | 48% | $18.70 | $224.40 |
| 60 months (5 yr) | 60% | $23.40 | $280.80 |
| 120 months (10 yr) | 120% | $46.80 | $561.60 |
Even a modest delay compounds: because the penalty never ends, a 10-year gap adds well over a thousand dollars a year, indefinitely. The lesson is simple — enroll in a Part D plan during your Initial Enrollment Period unless you already have creditable coverage.
How to avoid the penalty
You owe nothing for any month you had creditable drug coverage — coverage at least as good as standard Part D. That includes employer or union group plans, TRICARE, VA health benefits, and most COBRA plans with drug benefits. If you're working past 65 with employer coverage, confirm in writing that it's creditable before delaying Part D, and keep the annual notices your insurer sends as proof. For the full rules — coverage phases, the $2,100 out-of-pocket cap, the $35 insulin cap, and enrollment windows — see our complete guide to Medicare Part D. Related: IRMAA Part D surcharges stack on top of this penalty for higher earners — estimate those with our IRMAA calculator.