Last verified: April 19, 2026.
Enrollment
Medicare uses a small number of named enrollment windows. Each window controls what you can do without medical underwriting, without late penalties, and without a special qualifying event. Missing the right window almost always costs money for the rest of your life through a permanent late enrollment penalty.
The most consequential windows are the Initial Enrollment Period around your 65th birthday and the Medigap Open Enrollment Period that opens on the first day of the month you are both 65 and enrolled in Part B. After those, the Annual Enrollment Period in the fall is the routine yearly chance to change Medicare Advantage and Part D plans.
Enrollment periods
Your seven-month window around your 65th birthday.
Six-month one-time window for guaranteed-issue Medigap.
October 15 through December 7 each year, for Medicare Advantage and Part D.
January 1 through March 31, for Medicare Advantage enrollees only.
January 1 through March 31, for people who missed their IEP for Part B.
Triggered by qualifying life events such as loss of employer coverage.
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Not insurance advice specific to you. The information on this site is general educational content and is not insurance, legal, tax, or financial advice. Coverage rules, premiums, and program features change. Always verify current details with the official source listed on each page and with a licensed professional in your state before making a decision.
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