Window by birthday
| Born | Part A starts | Sign-up window |
|---|---|---|
| Jan 1, 1961 | Dec 1, 2025 | Sep 2025 – Mar 2026 |
| Jan 2, 1961 | Jan 1, 2026 | Oct 2025 – Apr 2026 |
| Mar 31, 1961 | Mar 1, 2026 | Dec 2025 – Jun 2026 |
| Jul 1, 1961 | Jun 1, 2026 | Mar 2026 – Sep 2026 |
| Jul 15, 1961 | Jul 1, 2026 | Apr 2026 – Oct 2026 |
| Dec 1, 1961 | Nov 1, 2026 | Aug 2026 – Feb 2027 |
A birthday on the 1st moves everything one month earlier: you are 65 on the last day of the month before your birthday.
How the dates are worked out
- You reach 65 the day before your 65th birthday. Premium-free Part A starts on the 1st of the month you reach 65 (42 CFR 406.10) — for a birthday on the 1st, that is the month before (Medicare.gov).
- The Initial Enrollment Period runs from 3 months before that month to 3 months after it, 7 months in all (42 CFR 407.14). Your Part B eligibility is tied to the day Part A starts (407.14(a)(2)).
- Part B: sign up in the first 3 months → coverage starts the month Part A does. Sign up in that month or any of the 3 after → coverage starts the month after you sign up (407.25(a)(2), for eligibility from 2023 on; earlier, coverage started 1 to 3 months later — 407.25(a)(1)).
What this page doesn't cover
- Medicare through disability or end-stage renal disease, and automatic enrollment when you already get Social Security
- Special Enrollment Periods for people still covered by an employer plan, and the late enrollment penalty amount
- Premiums, Medigap, and Medicare Advantage or Part D enrollment windows
This is an estimate, not advice. Confirm with Medicare.gov or Social Security. To compare when to start retirement benefits, see the Social Security claiming age calculator.
Frequently asked questions
When is my Medicare Initial Enrollment Period?
It is 7 months long: the 3 months before the month you turn 65, that month, and the 3 months after (42 CFR 407.14). Turning 65 in June means March through September, with June in the middle.
If I sign up in the month I turn 65, when does Part B start?
The first of the next month. Since 2023, signing up in the first 3 months of the window starts Part B in the month you turn 65; signing up in that month or the 3 months after starts it the month after you sign up (42 CFR 407.25).
My birthday is on the 1st. Is my window different?
Yes. You are considered 65 the day before your birthday, so premium-free Part A starts the month before your birthday month (Medicare.gov), and the 7-month window shifts one month earlier with it.
What if I miss the Initial Enrollment Period?
You can sign up during the General Enrollment Period, January 1 to March 31 each year, with coverage starting the month after you sign up — and you may owe a late enrollment penalty for as long as you have Part B, unless you qualify for a Special Enrollment Period.