Part B Late-Enrollment Penalty Calculator
The Medicare Part B late-enrollment penalty adds 10% to your premium. You owe that 10% for each full 12-month period you could have had Part B and did not take it. The standard premium is $202.90 a month in 2026. You pay the penalty for as long as you have Part B. Months covered by a current employer's plan do not count.
This page estimates what a gap in Part B coverage adds to your monthly premium. Choose how long you went without Part B after your Initial Enrollment Period ended — years from a dropdown, plus months — and it counts the full twelve-month periods in that delay, multiplies each by ten percent, and shows the resulting percentage, the amount added each month at this year's standard premium ($202.90), your new monthly total, and the yearly cost.
Two details the arithmetic makes visible: only full twelve-month periods count, so a delay under a year returns no penalty yet; and because the percentage is reapplied to whatever the standard premium is each year, the dollar amount grows as premiums do.
It needs only that length of delay (up to fifteen years and eleven months) — no income or health questions. An optional form asks for contact details if you want an advisor to call.
Before you calculate anything, the page states the main exception: months when you or your spouse had coverage through an active employer do not count, because they carry a Special Enrollment Period with an eight-month window — though COBRA and retiree coverage do not qualify. Your real figure may be smaller, or zero.
This is an estimate, not a bill. Social Security determines the actual penalty from your enrollment record, and Part D carries a separate penalty of its own. The page cannot enroll you or quote a plan; it also notes that the General Enrollment Period runs January 1 through March 31.
Frequently asked questions
How is the Part B late-enrollment penalty calculated?
Count the full 12-month periods you went without Part B after your Initial Enrollment Period ended. Multiply that count by 10%. Apply the result to the standard Part B premium. Partial years do not count at all.
Who does not owe a Part B late-enrollment penalty?
People covered by their own or a spouse's active employer group health plan. They enroll during the eight-month Special Enrollment Period that follows the end of that coverage. COBRA and retiree coverage do not qualify.
Does the Part B penalty ever go away?
For most people, no. It is added to the Part B premium for as long as they have Part B. And because it is a percentage, the dollar amount rises whenever the standard premium rises.
When can I enroll if I missed my window?
During the General Enrollment Period, which runs January 1 through March 31. Coverage then starts the first of the month after you enroll.
Updated September 15, 2026. Dollar figures are 2026 plan-year amounts transcribed from CMS publications and last verified by IM65 against the source for each: Parts A & B premiums, deductibles and IRMAA (August 11, 2026).