Medicare Part D Late Enrollment Penalty Calculator

The Part D penalty is 1% of the National Base Beneficiary Premium (NBBP) for each full month you went without Part D or other creditable drug coverage after becoming eligible. It’s rounded to the nearest $0.10 and added to your plan premium as long as you have Part D.

Select the year to auto-fill the NBBP (base premium used in the formula)
This picks a typical base automatically (you can override it below).
Auto-filled from your selection; enable manual override if needed.
Count only full months after your initial eligibility.
Use this if you want to enter a different base amount for your scenario.
If you qualify for Extra Help, the Part D penalty generally does not apply.

Results

Formula: Penalty = months uncovered × 1% × NBBP, rounded to nearest $0.10.