Free calculator
Part B late enrolment penalty calculator
Miss your Part B window and Medicare adds 10% to the premium for every full year you waited — and keeps adding it for as long as you hold Part B. This works out how much.
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- Shows the arithmetic
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How late were you, and what does that cost?
Your Part B penalty
$37.00 a month, for life
2 full years late is a 20% surcharge, added to your Part B premium for as long as you hold Part B.
- Months eligible but not enrolled
- 30 months
- Full 12-month periods
- 2 (part periods do not count)
- Penalty rate
- 20% of the standard premium
- Standard Part B premium
- $185.00 a month
- Monthly penalty
- $37.00
- Part B premium with the penalty
- $222.00 a month
- Extra over a year
- $444.00
The surcharge is recalculated each year against the new standard premium, so it rises as the premium rises.
The rule
10% for each full year, added for life
The penalty is not a fine you pay once. It is a permanent surcharge bolted onto your monthly Part B premium, and it is recalculated each January against whatever the new standard premium is.
Monthly penalty = standard Part B premium × 10% × full 12-month periods late
Two details do most of the damage. Part periods are thrown away, so eleven months late costs nothing and twelve months costs 10% forever. AndCOBRA is not employer coverage — every month on COBRA after 65 counts against you unless a Special Enrolment Period covers it.
| Full years late | Penalty rate | Added each month | Part B premium | Added each year |
|---|---|---|---|---|
| 0 | 0% | $0.00 | $185.00 | $0.00 |
| 1 | 10% | $18.50 | $203.50 | $222.00 |
| 2 | 20% | $37.00 | $222.00 | $444.00 |
| 3 | 30% | $55.50 | $240.50 | $666.00 |
| 4 | 40% | $74.00 | $259.00 | $888.00 |
| 5 | 50% | $92.50 | $277.50 | $1,110.00 |
| 6 | 60% | $111.00 | $296.00 | $1,332.00 |
| 7 | 70% | $129.50 | $314.50 | $1,554.00 |
| 8 | 80% | $148.00 | $333.00 | $1,776.00 |
| 9 | 90% | $166.50 | $351.50 | $1,998.00 |
| 10 | 100% | $185.00 | $370.00 | $2,220.00 |
Before you panic
What people ask about this penalty
For most people, no. It is added to the Part B premium for as long as you hold Part B. The two common exits are qualifying for a Medicare Savings Program, which pays the premium and the penalty, or having had a Special Enrolment Period all along and proving it with form CMS-L564.
Not if the employer had 20 or more staff and the cover came from current work — yours or your spouse's. Those months are protected by a Special Enrolment Period. COBRA and retiree plans are not active employer cover, so those months do count against you.
The rule counts full 12-month periods only, and part periods are discarded. Eleven months late is a 0% penalty; twelve months late is 10% for life. It is the single sharpest cliff in the programme.
The surcharge is recalculated every year against the new standard premium, so it rises as the premium rises. A 20% penalty set years ago is 20% of this year's premium, not of the premium when it started.
2026 plan year
The figures this calculator uses
Sample figures for the 2026 plan year. Medicare and the Marketplace reset these every autumn.
- Standard Part B premium (2026 sample)
- $185.00 a month
- Penalty rate
- 10% for each full 12 months
- How long it lasts
- For as long as you hold Part B
Every figure above is a sample for the 2026 plan year on a demonstration site. Medicare publishes the real ones each autumn at Medicare.gov, and they change every year.