Medicare has multiple enrollment periods with confusingly similar names. Here's what each one means and when it applies.
IEP — Initial Enrollment Period
- For people NEW to Medicare
- 7-month window: 3 months before, the month of, and 3 months after your 65th birthday
- Used to enroll in Part A, Part B, AND Part D and/or Medicare Advantage if desired
- Coverage starts the first day of your birthday month if you sign up in the 3 months before
- Late enrollment for Part B and Part D triggers permanent monthly penalties if you don't have other creditable coverage
ICEP — Initial Coverage Election Period (specific to Medicare Advantage)
- For people who become eligible for Medicare and want to choose Medicare Advantage at the same time
- 7-month window aligned with your IEP
- Specifically for ENROLLING IN AN MA PLAN at first eligibility
- After ICEP ends, you can only join MA during AEP or qualifying SEPs
In practice, most people experience IEP and ICEP simultaneously — they enroll in Part A, Part B, AND optionally an MA plan all in the same window. The distinction matters mostly for paperwork and CMS tracking.
AEP — Annual Enrollment Period
- For people ALREADY enrolled in Medicare
- October 15 – December 7 every year
- Switch from Original Medicare to Medicare Advantage, or vice versa
- Switch from one MA plan to another
- Switch from one Part D plan to another, or add Part D
- Drop Part D (rarely a good idea)
- Changes effective January 1 of the following year
OEP — Medicare Advantage Open Enrollment Period
- For people ALREADY enrolled in a Medicare Advantage plan
- January 1 – March 31 every year
- Switch to a different MA plan ONCE during this window, or
- Return to Original Medicare (and add Part D and Medigap if eligible)
- NOT for switching from Original Medicare to MA — that requires AEP
- NOT a second AEP — only one switch allowed
- Medigap during OEP usually requires medical underwriting (no guaranteed issue unless you're within your 6-month Medigap Open Enrollment from your IEP)
GEP — General Enrollment Period
- For people who MISSED their IEP and don't have other creditable coverage
- January 1 – March 31 every year
- Used to enroll in Part B (and Part A if not already)
- Coverage starts the month after enrollment
- Late enrollment penalty applies and is permanent
SEP — Special Enrollment Periods
- For people who experience qualifying life events anytime during the year
- 60-day to 8-month windows depending on the event
- Common triggers: lost employer coverage, moved to new area, plan exited your area, gained/lost Medicaid, recently released from incarceration, became dual-eligible
- Coverage and enrollment options vary by SEP type
Medigap Open Enrollment
- 6-month window starting the month you turn 65 AND are enrolled in Medicare Part B
- During this window, you have guaranteed-issue rights for any Medigap policy in your state
- No medical underwriting, no health questions, no pre-existing condition surcharges
- This window does NOT repeat. Outside of it, most states allow underwriting.
Birthday rule and other state-specific Medigap windows
- Some states (CA, OR, ID, IL, NV, LA, OK, MD) have annual birthday windows for switching Medigap with guaranteed issue
- Some states (NY, CT, MA, VT) have year-round Medigap protections
Cheat sheet of when to use each:
| Situation | Window |
|---|---|
| Newly eligible at 65 | IEP (7-month window around birthday) |
| Newly eligible and want MA | ICEP (same as IEP) |
| Newly eligible and want Medigap | Medigap Open Enrollment (6 months from Part B start) |
| Already on Medicare, want to change MA or Part D | AEP (Oct 15 – Dec 7) |
| Already on MA, want to switch to different MA or back to Original | OEP (Jan 1 – Mar 31) |
| Missed IEP, no creditable coverage | GEP (Jan 1 – Mar 31) |
| Lost employer coverage | SEP (8-month window for Part B, 63-day for Part D) |
| Plan exited your area | SEP + guaranteed-issue Medigap (Dec 8 – end of February) |
| First 12 months on MA, want to switch to Medigap | Trial right (guaranteed-issue Medigap) |
| Annual Medigap switching (in qualifying states) | Birthday rule window |
What to do next: Call (866) 534-1886. We confirm exactly which window applies to your situation and what enrollment options are available. Don't risk a permanent late-enrollment penalty by missing a window — free help. (866) 534-1886.