Free calculator
Part D late enrolment penalty calculator
Part D counts single months, not whole years. Every month without creditable drug coverage adds 1% of the national base premium — and it stays on the bill for as long as you hold a drug plan.
- No email wall
- Counts single months
- Shows the arithmetic
Run the numbers
How many months were you uncovered?
Your Part D penalty
$10.70 a month, for life
Every full month without creditable drug cover adds 1% of the national base premium, and the surcharge stays for as long as you hold Part D.
- Full months without creditable drug cover
- 29 months
- Penalty rate
- 1% × 29 = 29%
- National base beneficiary premium (2026 sample)
- $36.78 a month
- Monthly penalty, rounded to the nearest 10¢
- $10.70
- Extra over a year
- $128.40
Unlike Part B, this one counts single months, not whole years — and it is recalculated each year against the new base premium.
The rule
1% a month, against a national figure
The penalty is not a percentage of your drug plan premium. It is a percentage of a single national figure, which is why two people on very different plans can owe exactly the same surcharge.
Monthly penalty = national base beneficiary premium × 1% × full uncovered months
Medicare rounds the result to the nearest ten cents, then adds it to whatever your plan charges. Because the national figure is reset each year, the penalty moves with it — a 29% surcharge is 29% of this year's base, not of the base when the gap happened.
| Uncovered months | Penalty rate | Added each month | Added each year |
|---|---|---|---|
| 3 | 3% | $1.10 | $13.20 |
| 6 | 6% | $2.20 | $26.40 |
| 12 | 12% | $4.40 | $52.80 |
| 18 | 18% | $6.60 | $79.20 |
| 24 | 24% | $8.80 | $105.60 |
| 29 | 29% | $10.70 | $128.40 |
| 36 | 36% | $13.20 | $158.40 |
| 48 | 48% | $17.70 | $212.40 |
| 60 | 60% | $22.10 | $265.20 |
The awkward questions
What people ask about this penalty
A plan the insurer expects to pay at least as much as standard Part D. Most employer, union, VA and TRICARE drug benefits qualify. The plan must tell you in writing every autumn — keep that letter, because it is the only thing that clears the penalty later.
Usually yes. The cheapest Part D plan in most counties costs less per month than the penalty you would owe after a couple of years without one, and the surcharge never stops once it starts.
Different statutes, different maths. Part B discards part years; Part D charges 1% per month from the first month. Two months late costs something here and nothing under Part B.
Yes, in three situations: you qualify for Extra Help, which wipes it out; you can prove the gap was covered by a creditable plan; or you ask for a reconsideration within 60 days of the letter telling you the penalty applies.
2026 plan year
The figures this calculator uses
Sample figures for the 2026 plan year. Medicare and the Marketplace reset these every autumn.
- National base beneficiary premium (2026 sample)
- $36.78 a month
- Penalty rate
- 1% for each full uncovered month
- Rounding
- To the nearest 10 cents
Every figure above is a sample for the 2026 plan year on a demonstration site. Medicare publishes the real ones each autumn at Medicare.gov, and they change every year.