Medicare Part B Late Enrollment Penalty Calculator
Enter how many months you went without Part B when you could have had it. See the percentage, what it adds to the $202.90 premium every month, and the total over the years you expect to have Medicare.
Your numbers
Count from the end of your Initial Enrollment Period (or Special Enrollment Period) to the month coverage finally starts. Time on a current employer plan with 20+ employees does not count.
Real cost is higher: the penalty is recalculated each year against that year’s premium, which has risen most years.
What late enrollment costs
All figures at the 2026 standard premium of $202.90. Twenty years of Part B is a normal expectation at 65.
| Months late | Full 12-month periods | Penalty | Per month | Per year | 20 years |
|---|---|---|---|---|---|
| 11 | 0 | 0% | $0.00 | $0 | $0 |
| 14 | 1 | 10% | $20.29 | $243 | $4,870 |
| 26 | 2 | 20% | $40.58 | $487 | $9,739 |
| 38 | 3 | 30% | $60.87 | $730 | $14,609 |
A 24-month gap over 25 years of Medicare: $40.58 a month, $12,174 total at today’s premium, more as premiums rise.
How the math works
Count the full 12-month periods you were eligible for Part B and not enrolled, excluding months covered by a current employer plan (20+ employees). Multiply that count by 10%. Multiply the percentage by the standard premium for the year to get the monthly penalty. It never expires; when the standard premium changes each January, the penalty is recomputed against the new figure. The tool multiplies the 2026 monthly penalty by 12 and by the years you enter, which understates the real total because it holds the premium flat.
The way people actually end up here: they keep COBRA or retiree coverage past 65 believing it protects them, or they retire at 66 and assume there is a grace period. Neither is true. Only current employment coverage delays the clock, and the Special Enrollment Period is 8 months from the month the job or the coverage ends, whichever comes first.
Sources
This tool is educational and simplifies by design. It computes published Medicare rules for the inputs you enter; it does not know your full situation, is not insurance, tax, or legal advice, and does not recommend any action. Nothing you type is transmitted or stored — the math runs in your browser. Confirm your dates and amounts with Social Security (1-800-772-1213), Medicare (1-800-MEDICARE), or a licensed professional before acting.
Penalty questions, answered
Does the penalty ever go away?
No. The Part B penalty is added for as long as you have Part B. Because it is a percentage of that year’s standard premium, it grows every time the premium rises.
What counts as a “full 12-month period”?
Months after your Initial Enrollment Period ended (or your Special Enrollment Period ended) during which you could have had Part B but did not. Eleven months late means no penalty; fourteen months means one period, 10%.
I was covered by my employer plan. Does that time count?
Not if it was current employment coverage from an employer with 20 or more employees (yours or your spouse’s). That time is excluded and you get an 8-month Special Enrollment Period when it ends. COBRA and retiree coverage do count as uncovered months.
Is there a similar penalty for Part A?
Only for people who have to buy Part A (fewer than 40 quarters of Medicare taxes). It is 10% for twice the number of years you delayed, not for life.
Related tools and guides
Part D penalty calculator
The drug-coverage penalty is smaller per month but starts after only 63 uncovered days.
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Your exact Initial Enrollment Period, Special Enrollment Period, and Medigap window from your birth date.
Open the tool →Still-working checker
Which rules apply if you or your spouse is still employed at 65.
Open the tool →
Talk it through before you decide
Bring your birth date, your work situation, and last year’s tax return. Leave knowing your enrollment window, what Medicare will cost you, and whether the income surcharge applies.
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