Tool · Late Enrollment Penalty Calculator
What does “late” actually cost?
Part B penalty
10% added to your Part B premium for every full 12 months you went without Part B (when you should have had it).
Part D penalty
1% of the national base beneficiary premium for every month you went without creditable drug coverage. CMS rounds the penalty to the nearest $0.10.
The Part D penalty is recalculated each year because the national base beneficiary premium can change.
Over 20 years
$11,995
That’s how much these penalties could pull out of your pocket over a typical retirement. And that’s before the base premium even goes up — which it does, most years.
How to avoid it
Enroll during your Initial Enrollment Period (the 7 months around your 65th birthday), or be sure you have creditable coverage from an employer with 20+ employees. Get proof in writing.
COBRA doesn’t count
One of the most expensive misunderstandings. For Part B, COBRA and retiree coverage don’t count as active employer coverage, so they don’t earn you a Special Enrollment Period, and your penalty clock keeps ticking. For Part D it depends: many retiree drug plans are creditable (check the plan’s annual notice), but COBRA often isn’t. Get it in writing either way.
Want Adam to review this with you?
I told you I wouldn’t hold your results hostage.
If you want help applying this to your actual doctors, prescriptions, ZIP code, budget, and timing, you can book a 30-minute review.
Review My Results with Adam →Estimate uses 2026 figures (Part B base $202.90, Part D national base $38.99). The penalty is recalculated annually as the base premium changes.