If you are approaching Medicare age or are already enrolled, you’ve probably heard many terms like AEP, OEP, and SEP. It’s quite confusing! Let’s jump in.
1. Initial Enrollment Period (IEP) – Your Medicare “Welcome Window”
This is your first chance to sign up for Medicare when you turn 65.
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- It starts 3 months before your 65th birthday
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- It includes your birthday month
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- And ends 3 months after your birthday
That gives you 7 months to enroll in Medicare Part A and Part B.
Tip: If you’re still working and have employer coverage, you might not need to sign up for Part B immediately. (Talk to an agent before deciding.)
2. Annual Enrollment Period (AEP) – The Big One
This happens every year from October 15 to December 7.
During AEP, anyone on Medicare can:
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- Switch from Original Medicare to a Medicare Advantage plan (Part C)
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- Switch from Medicare Advantage back to Original Medicare
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- Join, drop, or change a Part D drug plan
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- Or switch from one Medicare Advantage plan to another
Whatever changes you make will take effect January 1st.
3. Medicare Advantage Open Enrollment Period (OEP) – One More Shot
This is for people already enrolled in a Medicare Advantage plan.
It runs from January 1 to March 31 each year.
During OEP, you can:
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- Switch to another Medicare Advantage plan
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- Or go back to Original Medicare (and possibly add Part D)
You can’t join a Medicare Advantage plan for the first time during this window; you can only switch or drop.
4. Special Enrollment Periods (SEPs) – Life Happens
SEPs are triggered by specific life events, like:
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- You retire and lose employer coverage
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- You move out of your plan’s service area
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- You qualify for Medicaid or Extra Help
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- Or your plan drops coverage in your area
These events open a temporary window (usually 2–3 months) for you to make changes.
5. General Enrollment Period (GEP) – For Late Starters
If you missed your Initial Enrollment Period and don’t qualify for a SEP, you can sign up for Medicare Part A and/or B from January 1 to March 31 each year.
But coverage doesn’t start until July 1, and you might have a penalty for enrolling late.
Quick Recap
| Enrollment Period | Who it is for | When it Happens | What You Can Do |
| IEP Initial Enrollment Period |
Turning 65 | 3 months before to 3 months after one’s birthday month | Enroll in Parts A & B |
| AEP Annual Enrollment Period |
Anyone on Medicare | Oct 15 – Dec 7 | Change Medicare Advantage or Prescription Drug Plans |
| OEP Open Enrollment Period |
Advantage enrollees | Jan 1 – Mar 31 | Switch or drop Medicare Advantage Plan |
| SEP Special Enrollment Period |
Based on life events | Varies | Make plan changes |
| GEP General Enrollment Period |
Late enrollers | Jan 1 – Mar 31 | Sign up for Parts A & B |