Medicare Enrollment Periods Explained
May 20, 2026
Quick Answer: Medicare Enrollment Periods at a Glance
Medicare has five enrollment windows, each tied to a different life stage: turning 65 (IEP), missing your IEP (GEP), losing coverage (SEP), comparing plans each fall (AEP), and adjusting your Advantage plan early in the year (MA OEP).
| Window | When | What You Can Do |
|---|---|---|
| IEP — Initial | 7 months around 65th birthday | Enroll in Parts A, B, D; pick Advantage or Medigap |
| GEP — General | Jan 1 – Mar 31 | Sign up if you missed IEP (penalties may apply) |
| SEP — Special | Triggered by life event | Enroll after losing employer coverage, moving, etc. |
| AEP — Annual | Oct 15 – Dec 7 | Switch Advantage / Part D plans for next year |
| MA OEP | Jan 1 – Mar 31 | One Advantage-plan change or drop to Original Medicare |
- What if I keep working past 65?
- Qualifying employer coverage usually grants an 8-month Special Enrollment Period after you (or your spouse) stop working — no penalty.
- Can I change Medigap plans during AEP?
- AEP doesn't apply to Medigap. Outside your one-time Medigap Open Enrollment, switching may require medical underwriting (varies by state).
- Does losing a spouse trigger a SEP?
- It can — if you lose employer coverage tied to your spouse, you generally get an 8-month SEP to enroll in Part B without penalty.
Medicare enrollment periods, all in one place.
IEP, AEP, MA OEP, SEP, GEP, and Medigap Open Enrollment. Each is a different window. Here is what each one allows.
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Initial Enrollment Period (IEP)
7 months around your 65th birthday. Most people enroll here. See our Turning 65 timeline.
Annual Enrollment Period (AEP)
October 15 to December 7 each year. You can switch Advantage plans, switch Part D plans, or move between Original Medicare and Advantage. Changes take effect January 1.
Medicare Advantage Open Enrollment (MA OEP)
January 1 to March 31. One chance for current Advantage enrollees to switch Advantage plans or move back to Original Medicare + Part D.
Special Enrollment Periods (SEPs)
Triggered by qualifying life events:
- Moving out of your plan's service area
- Losing employer or union coverage
- Qualifying for Extra Help or Medicaid
- Plan terminating or contract change
General Enrollment Period (GEP)
January 1 to March 31. For people who missed their IEP and do not qualify for an SEP. Part B coverage starts the month after enrollment, and late penalties may apply. See our late penalty guide.
Medigap Open Enrollment
A one-time 6-month window starting the month you are 65 AND enrolled in Part B. During this window, Medigap carriers cannot use medical underwriting. Outside this window, most states allow underwriting — see switching from Advantage to Medigap.
Frequently asked questions
When can I switch Medicare plans?
Most people switch during AEP (Oct 15 – Dec 7) or MA OEP (Jan 1 – Mar 31) depending on what they want to switch. SEPs cover qualifying life events.
What happens if I miss my Initial Enrollment Period?
You can use the General Enrollment Period (Jan 1 – Mar 31) but coverage does not start until the month after enrollment and late penalties may apply for life.
Can I switch from Medigap to Medicare Advantage?
Yes, during AEP. You can drop Medigap at any time, but getting a new Medigap policy later may require medical underwriting outside your initial Medigap Open Enrollment.