How the penalty works
The penalty is 10% of the standard Part B premium for each full 12 months you could have had Part B but didn't. Partial years don't count: 23 months late is one 12-month period, so 10%. Because it's figured on the standard premium, the dollar amount rises each year when the premium does. If you also pay IRMAA, the penalty is still figured on the standard premium.
When there's no penalty
- You signed up during your Initial Enrollment Period, the 7 months around your 65th birthday.
- You or your spouse had group health coverage from current work, and you signed up within 8 months after the work or the coverage ended.
- You get help with Part B costs through a Medicare Savings Program.
COBRA, retiree coverage and coverage from a past job don't count as current work. Medicare enrollment periods.
Questions
How is the Part B late enrollment penalty calculated?
10% of the standard Part B premium for each full 12-month period you could have had Part B but didn't sign up. Medicare's example: 24 months late is a 20% penalty, so in 2026 you'd pay about $243.50 a month instead of $202.90.
Is the Part B penalty forever?
In most cases, yes: you pay it for as long as you have Part B. People who get help paying Part B through a Medicare Savings Program generally don't pay it.
How do I avoid the Part B penalty?
Sign up in your Initial Enrollment Period around 65, or within 8 months after job-based coverage from current work (yours or your spouse's) ends. Coverage from a past job, COBRA or retiree plans doesn't count as current work.
Updated November 6, 2026. Sources: Medicare.gov, Enrolling in Medicare Part A & Part B; CMS, 2026 Medicare Parts A & B Premiums and Deductibles; 42 U.S.C. 1395r(b). Estimates, not legal advice. Not affiliated with Medicare.