Medicare Part D Late Enrollment Penalty Calculator
If you don't sign up for Medicare Part D (prescription drug coverage) when you're first eligible, and you go 63 or more consecutive days without creditable drug coverage, you'll pay a penalty added to your Part D premium for as long as you have Medicare drug coverage.
The Part D penalty is calculated as 1% of the national base beneficiary premium × the number of months you went without creditable coverage. In 2025, the base premium is $36.78/month. Even a modest delay — say 24 months — results in a 24% surcharge on top of your plan's monthly premium.
The good news: many employer plans and TRICARE qualify as creditable drug coverage, protecting you from penalties even if you delay enrollment. Use the calculator below to estimate your penalty, and contact Scott if you need help determining whether your current coverage is creditable.
Frequently Asked Questions
How is the Part D penalty calculated?
The penalty equals 1% of the CMS national base beneficiary premium multiplied by the number of months you lacked creditable drug coverage. In 2025, that base is $36.78. If you went 18 months without creditable coverage, your penalty is 18% × $36.78 = $6.62/month added to your Part D premium, rounded to the nearest $0.10.
What counts as creditable prescription drug coverage?
Creditable coverage is drug coverage that is expected to pay, on average, at least as much as Medicare's standard Part D plan. This includes coverage from an employer or union, TRICARE, VA benefits, FEHB, CHIP, or certain other programs. Your plan should send you a "Notice of Creditable Coverage" each fall — keep this document.
Is the Part D penalty permanent?
The penalty lasts as long as you have Medicare drug coverage, with one exception: if you qualify for Extra Help (Low Income Subsidy), your penalty may be reduced or waived. The dollar amount of the penalty changes each year as the base premium is updated.
What is the 63-day rule for Part D?
You can go up to 63 consecutive days without creditable prescription drug coverage without triggering a penalty. If your coverage gap exceeds 63 days, the entire uncovered period counts toward your penalty — not just the days beyond 63.
Can I get Part D through a Medicare Advantage plan?
Yes. Most Medicare Advantage plans include prescription drug coverage (called MAPD plans). Enrolling in a Medicare Advantage plan with drug coverage satisfies the Part D requirement and avoids late enrollment penalties. Scott can compare MAPD and standalone Part D plan options for your specific medications.
Have Questions? Talk to Scott.
Scott is a licensed Medicare broker in Eugene, Oregon. No sales pressure — just honest guidance.