Medicare's late-enrollment penalties are permanent premium increases. We apply the official penalty formulas to how late you were (or would be), then total the extra cost over the years you expect to have Medicare.

Step by step

1. Part B: the penalty is 10% of the standard Part B premium for each FULL 12-month period you went without Part B after your window closed — 26 months late is two full periods, so 20%.
2. Part D: the penalty is 1% of the national base beneficiary premium for each month without creditable drug coverage, rounded to the nearest 10 cents.
3. Both penalties are added to your premium every month for as long as you have the coverage.
4. The lifetime figure is the combined monthly penalty × 12 × the years you expect to have Medicare, at the 2026 premium levels.

The math

partB = floor(monthsLate ÷ 12) × 10% × standardPartBPremium; partD = round(monthsWithoutCoverage × 1% × nationalBasePremium, nearest $0.10); lifetime = (partB + partD) × 12 × yearsOnMedicare.

Sources & assumptions

• Medicare.gov — "Part B late enrollment penalty" and "Part D late enrollment penalty".
• CMS annual premium announcements (the standard Part B premium and Part D national base beneficiary premium).

Note: Nothing proprietary — these are Medicare's published penalty formulas.

1. This is an educational estimate of Medicare late-enrollment penalties, not an official penalty determination.
2. Penalties are recalculated each year against that year's premiums; this estimate holds the 2026 figures level, so the true lifetime cost grows as premiums do.
3. Creditable employer coverage usually lets you delay without penalty — COBRA and retiree coverage generally do NOT count for Part B. Confirm your situation with Medicare or Social Security.
4. This tool is not affiliated with or endorsed by Medicare, CMS, or any government agency.