How much is the Medicare Part B late enrollment penalty?

The penalty only applies if you went without Part B and without creditable coverage from current employment. If you kept working past 65 and had group health coverage through your own or your spouse’s active employer, you can delay Part B with no penalty at all. When that employment or coverage ends, you get an 8-month Special Enrollment Period to sign up penalty-free. COBRA and retiree coverage do not count as creditable for this purpose, which is where many people get tripped up.

How the penalty adds up in 2026

The penalty is 10% of the standard Part B premium for each full 12-month period you were eligible but not enrolled. For 2026, the standard premium is $202.90 per month, so each full year of delay adds about $20.29. Medicare rounds the total to the nearest ten cents.

Only full 12-month periods count. A 26-month delay counts as two periods, not three.

A worked example

Say your Initial Enrollment Period ended in March 2023, you had no creditable employer coverage, and you finally enrolled during the General Enrollment Period in early 2026. That is roughly a 34-month gap, which counts as two full 12-month periods. Your penalty is 20% of the standard premium. For 2026 that is about $40.58 on top of $202.90, so you pay roughly $243.50 per month.

The penalty is not a one-time fee and it does not expire. It is recalculated against each year’s standard premium, so as the premium rises over time, the dollar amount of your penalty rises with it, for as long as you keep Part B.

Who never pays it

You generally will not owe the penalty if you enroll during your 7-month Initial Enrollment Period around your 65th birthday, or during the 8-month Special Enrollment Period after losing employer coverage based on active employment. People with certain Medicaid or Medicare Savings Program help may also have the penalty waived, depending on their situation.

Here’s the mistake I see people make most often: assuming COBRA buys them more time. It does not, and the 8-month clock starts when the job-based coverage ends, not when COBRA runs out.