Medicare only lets you sign up or change plans during specific windows. Miss them and you can owe a permanent penalty. Here is every window, with 2026 dates.
Your 7-month window around your 65th birthday: the 3 months before your birthday month, your birthday month, and the 3 months after. This is when most people first enroll. Find yours with the sign-up window calculator.
October 15 – December 7 every year. This is when anyone with Medicare can join, switch, or drop a Medicare Advantage or Part D plan. Changes take effect January 1. This is the busiest window of the year. (See our AEP 2026 guide.)
January 1 – March 31. If you are already in a Medicare Advantage plan, you get one chance here to switch to a different Advantage plan or go back to Original Medicare.
January 1 – March 31 for people who missed their Initial Enrollment Period and don't qualify for a Special Enrollment Period. Coverage starts the month after you enroll — and a late penalty may apply.
Triggered by qualifying life events — losing employer coverage, moving, leaving a plan that ended, and more. These let you enroll or change outside the normal windows. The enrollment period finder tells you which window applies to your situation.
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New here? Start for $7.49 →The Annual Enrollment Period runs October 15 to December 7, 2026, with changes effective January 1, 2027.
AEP (Oct 15-Dec 7) is for everyone with Medicare. OEP (Jan 1-Mar 31) is only for people already enrolled in a Medicare Advantage plan.
No. You can only enroll or change during a valid window — your Initial period, AEP, the Advantage OEP, or a qualifying Special Enrollment Period.
Figures on this page are verified against U.S. government primary sources: