Compare IEP, AEP, OEP, and SEP windows, qualifying events, and key deadlines.
A side-by-side comparison of the core Medicare enrollment periods, their timing, and allowed actions.
| Period | When It Happens | Who Is Eligible | What You Can Do |
|---|---|---|---|
| IEP Initial Enrollment |
7-month window around your 65th birthday | Individuals turning 65 or qualifying by disability | Sign up for Part A, Part B, Medicare Advantage, and Part D |
| AEP Annual Enrollment |
October 15 – December 7 | Anyone already on Medicare | Switch Advantage plans, return to Original Medicare, join or change Part D |
| OEP Advantage Open |
January 1 – March 31 | Current Medicare Advantage enrollees only | Make one switch to another Advantage plan or return to Original Medicare + Part D |
| SEP Special Enrollment |
Triggered by qualifying life events (varies) | People experiencing specific life or coverage changes | Enroll or switch plans outside normal windows without penalty |
Life events that trigger a Special Enrollment Period (SEP) and exempt you from late penalties.
If you or your spouse retire or lose group health coverage from an employer with 20+ employees, you get an 8-month SEP to enroll in Medicare penalty-free.
Relocating to a new county or state outside your current plan's network triggers a 2-month window to select a plan in your new area.
If Medicare terminates your plan's contract or your insurer does not renew coverage for the upcoming year, you receive a dedicated SEP to switch plans.
Gaining or losing Medicaid or Medicare Extra Help eligibility gives you ongoing opportunities to adjust your Medicare Advantage or Part D plans.
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Find a Medicare Agent by ZIPGenerally you can only make one plan change per period, and each period serves a different purpose, so which one applies depends on your specific situation and timing.
AEP (Oct 15 – Dec 7) allows anyone to switch between Original Medicare, Advantage, or Part D. OEP (Jan 1 – Mar 31) is strictly for individuals already enrolled in a Medicare Advantage plan to make one switch.
Typically no. If you qualify for a genuine SEP and enroll within its window, Medicare waives late-enrollment penalties because the transition was due to a qualifying life event.
If you miss your IEP without qualifying employer coverage, you must wait until the General Enrollment Period (Jan 1 – Mar 31), and you may incur lifetime late penalties for Part B and Part D.
Yes. Between January 1 and March 31, you can drop your Medicare Advantage plan, switch back to Original Medicare, and enroll in a standalone Part D prescription drug plan.
Yes. If you move outside your plan's service area, you qualify for a Special Enrollment Period (usually 2 months) to switch to a plan available in your new location.
You typically have an 8-month window to enroll in Part A and Part B without penalty once employment or group health coverage ends (whichever happens first).
Any plan selections or changes made during AEP (October 15 through December 7) take effect on January 1 of the following year.
You can apply, but you are not guaranteed coverage unless you are in your 6-month Medigap Open Enrollment window or qualify for a federal guaranteed issue right.
No. COBRA and retiree health coverage are not considered coverage based on current employment, so they do not grant an SEP or waive late-enrollment penalties.