Guide

The Part B late-enrollment penalty, and how to avoid it

Figures and rules on this page last checked against their sources: October 25, 2026.

If you could have had Part B and didn't sign up, your premium can go up 10% for each full 12 months you waited. It is not a one-time fee. It is added to your premium every month, usually for as long as you have Part B.¹

To work out a figure for your own dates, use the penalty estimate.

How the months are counted

For people who first signed up on or after January 1, 2023, the count runs from the end of your Initial Enrollment Period to the end of the month you sign up. Months when a group health plan through your own or your spouse's current job covered you are left out.²

Different rules applied to sign-ups before 2023. The count ran to the end of the enrollment period you signed up in, so a sign-up in the General Enrollment Period counted through March 31, and Part B then started on July 1.³

Only full 12-month periods count.¹ Eleven months adds nothing. Twelve adds 10%. Twenty-three months is still 10%. Twenty-four is 20%.

Medicare.gov's worked example

Medicare.gov's example is someone who waited 2 full years, 24 months, without a Special Enrollment Period. The penalty is 20%. In 2026 that is 20% of the standard premium of $202.90 a month⁴, or $40.58, for a total of $243.48, which rounds to $243.50 a month.¹

A second example, through the General Enrollment Period

Say you turned 65 in June 2024 and had no job-based coverage. Your Initial Enrollment Period ended on September 30, 2024. You sign up in the General Enrollment Period, in March 2027.

Months from the end of September 2024 to the end of March 2027: 30.
Full 12-month periods in 30 months: 2.
Penalty: 20%.
Coverage starts April 1, 2027, the month after you sign up.⁵

Without a Special Enrollment Period, sign-ups after your first window are taken only from January 1 to March 31, so the month you sign up will be one of those three.⁵

A third example, with job coverage and a missed deadline

Now take someone with the same dates whose spouse's employer plan, through the spouse's current job, covered them from the time they turned 65 until the job ended in December 2025. Their 8-month Special Enrollment Period ran out at the end of August 2026. They missed it, so they too sign up in March 2027.

Months from the end of September 2024 to the end of March 2027: 30.
Months after the window ended that were covered through the spouse's current job, left out: 15 (October 2024 to December 2025).
Months that count: 15, which is one full 12-month period.
Penalty: 10%, not 20%.²

Missing the 8 months cost them the penalty-free sign-up and some months without coverage, but the months they were covered through work still don't count against them.

The penalty moves with the premium

The penalty is a percentage added to each year's standard premium, not a fixed dollar amount. When the standard premium changes, the penalty changes with it.¹

The 2027 standard premium had not been announced when this page was last checked.⁶

How to avoid it

Sign up in your Initial Enrollment Period if you have no job-based coverage. The seven months around your 65th birthday are the simplest route. See the Initial Enrollment Period, explained.
If current work covers you, yours or your spouse's, use the Special Enrollment Period: any time while covered, or within 8 months after the job or the coverage ends, whichever comes first.⁷
Don't count on COBRA or retiree coverage. Neither is coverage through current work, and COBRA doesn't extend the 8 months.⁸
Check the Medicare Savings Programs. They help people with limited income and resources pay Medicare costs, and Medicare.gov says you generally won't pay a Part B penalty if you enroll in one.⁹

If something outside your control made you miss it

Since January 1, 2023, Special Enrollment Periods have existed for exceptional situations. Medicare.gov lists a natural disaster or declared emergency, wrong or misleading information from your employer or health plan, release from incarceration, losing Medicaid, and other exceptional conditions you raise with Social Security.¹⁰

If you sign up within one of these, the months it covers are left out of the penalty count.²

The other two penalties

Part A. Most people get Part A without a premium and never face this one. If you have to buy Part A and don't when first eligible, the premium can go up 10%, and you pay the higher premium for twice the number of years you didn't sign up.¹¹

Part D. If you don't join a drug plan when you first get Medicare and go 63 days or more without creditable drug coverage, you pay an extra 1% for each month.¹² It is figured on the national base beneficiary premium: $38.99¹³ in 2026 and $41.33¹⁴ in 2027. Medicare.gov's example is 14 months late in 2026: 14% of $38.99, rounded to $5.50 a month, added to the plan's premium for as long as you have Medicare drug coverage.¹²

Questions to settle before you wait

Is the coverage I have now from current work, mine or my spouse's?
Does the employer have 20 or more employees? If not, does my plan expect me to have Part B?
When exactly does my job, or my coverage, end? What date is 8 months after that?
Is my drug coverage creditable, and do I have the notice that says so?

Free help with your own case: your State Health Insurance Assistance Program.¹⁵