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Your Medicare Enrollment Timeline
Medicare has five enrollment windows and each allows different changes. This tool places you in the right one. Your Initial Enrollment Period is 7 months — the 3 months before your 65th-birthday month, that month, and the 3 months after; the Annual Enrollment Period runs October 15 – December 7 every year.
The windows
| Window | When | What it allows |
|---|---|---|
| Initial Enrollment | 7 months — the 3 months before your 65th-birthday month, that month, and the 3 months after | Enrol in A, B, C, D; buy Medigap |
| Annual Enrollment | October 15 – December 7 | Change Advantage or Part D plans |
| Advantage Open Enrollment | January 1 – March 31 | One switch, or back to Original Medicare |
| General Enrollment | January 1 – March 31 | Enrol late in A/B, with penalty |
| Medigap Open Enrollment | the 6 months that begin the month you're 65 or older AND enrolled in Part B | Buy any Medigap with guaranteed acceptance |
Why the timing matters
Sign up in the first three months of your Initial Enrollment Period and coverage starts the first day of your birthday month. Later in the window and coverage is delayed. See when coverage starts.
The permanent penalties
Part B: 10% of the standard premium for each full 12-month period you could have had Part B but didn't. Part D: 1% of the national base beneficiary premium for each month you went without creditable drug coverage. Both last as long as you have the coverage. Estimate yours with our Part B and Part D tools.
Events that open a Special Enrollment Period
- Leaving coverage from active employment — 8 months after the employment or the group coverage ends, whichever comes first.
- Moving out of your plan's service area.
- Your plan leaving your county.
- Gaining or losing Medicaid or Extra Help.
Details on Medicare.gov.
The one that never comes back
Your Medigap window lasts the 6 months that begin the month you're 65 or older AND enrolled in Part B and does not repeat. After it, carriers may use medical underwriting in most situations — Medicare.gov.
Next steps
Read the full enrollment guide or check your eligibility.
Not sure which of these fits you? A free 15-minute call with a licensed local advisor sorts it out — no pressure, and no cost to you. We do not offer every plan available in your area. For a complete list of every plan in your county, use Medicare Plan Compare or call 1-800-MEDICARE.
Questions, answered
When can I first sign up for Medicare?
Your Initial Enrollment Period is 7 months — the 3 months before your 65th-birthday month, that month, and the 3 months after. Enrolling in the first three months means coverage starts the first day of your birthday month.
What if I missed my window?
Unless a Special Enrollment Period applies, you wait for the General Enrollment Period (January 1 – March 31) and pay a permanent Part B penalty.
Does the Annual Enrollment Period let me buy Medigap?
Not with a guarantee. AEP covers Medicare Advantage and Part D. Medigap has its own 6-month guaranteed window at 65.
Sources
- Medicare.gov — When can I sign up for Medicare?
- Medicare.gov — When does Medicare coverage start?
- Medicare.gov — Joining a plan
- Medicare.gov — When to buy a Medigap policy
Figures are for 2026 and come from the official sources above. Plan-specific costs vary by county and carrier — confirm yours on Medicare Plan Compare or with a licensed agent.
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Content reviewed by Brian Penner, Independent Medicare advisor — no pressure.