People who missed their chance to sign up for Medicare Part B, and who do not qualify for a special exception, get one more shot each year: the General Enrollment Period, which runs from January 1 through March 31. Unlike the seven-month window most people get around their 65th birthday, this one is a single, fixed block that repeats annually regardless of when in the prior year someone became eligible, and it comes with a cost most people would rather avoid — a monthly premium penalty that, for many, lasts the rest of their life on Medicare.
How the General Enrollment Period actually works
Anyone who did not sign up for Part A or Part B when first eligible, and does not qualify for a Special Enrollment Period, can enroll only between January 1 and March 31 each year, according to Medicare’s page on when coverage starts. Coverage then begins the month after enrollment — a change from the older rule, under which coverage could be delayed until July regardless of when during the window someone signed up. Someone who enrolls in January now gets coverage in February, rather than waiting months longer for the same application.
The General Enrollment Period exists specifically for people outside a Special Enrollment Period, which covers situations such as having current employer coverage through active work, losing Medicaid on or after 2023, or being affected by a declared natural disaster. Someone who has group health coverage through a current job, or a spouse’s job, generally has an 8-month Special Enrollment Period after that coverage or the employment ends — and using it avoids the penalty altogether, without waiting for the next General Enrollment Period. Other, lesser-known Special Enrollment Periods cover people who have TRICARE, who volunteer for an extended period in a foreign country, or who were released from incarceration on or after 2023 — each with its own start date, length and rules for when coverage begins, but all designed to avoid forcing someone into the January-through-March window and its accompanying penalty.
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The premium penalty tied to a missed window
Signing up during the General Enrollment Period after missing an earlier chance typically comes with a lifetime late-enrollment penalty on Part B: an extra 10 percent of the standard monthly premium for every full 12-month period a person could have signed up but did not, according to Medicare’s page on avoiding late-enrollment penalties. For someone who waited two full years, that penalty is 20 percent. Applied to the 2026 standard Part B premium of $202.90, a 20 percent penalty adds $40.58, bringing the monthly premium to $243.48 (rounded to $243.50) — and that surcharge is not a one-time fee. It is added to the premium for as long as the person has Part B, which for most people means indefinitely.
The penalty differs from the one attached to Medicare drug coverage, which is calculated separately and pegged to the national base beneficiary premium rather than the Part B premium, though both share the same basic design: a percentage add-on tied to how long someone went without qualifying coverage, recalculated each year as the underlying premium changes but never simply forgiven once it starts.
The Part B penalty math a late sign-up carries forward
Missing the seven-month window at 65 is a fact many people only discover once a Medicare bill already reflects the penalty, and working out exactly how many 12-month periods were missed — and whether a Special Enrollment Period applies instead — is not something most people calculate on their own before the next January-to-March window opens.
It is a 10-page kit with 51 state Medicare cost-help packs and the new Part D out-of-pocket cap.
See the yearly cost review and Open Enrollment dates in The Medicare Cost & Coverage Protection Kit.
This article was researched and drafted with the help of AI and reviewed by The Financial Wire editorial team before publication.
David M. Keller is a finance writer based in Columbus, Ohio, covering personal finance and consumer-focused economic topics. He earned his degree in journalism from Ohio University and began his career reporting on local business and economic trends for a regional media outlet. Since then, he has contributed to a variety of online publications, focusing on clear, practical coverage of topics such as cost of living, debt, and everyday financial decision-making.
