← All comparisons
Annual Enrollment vs Medicare Advantage Open Enrollment
Written by My65 Playbook Editorial Team
Last reviewed
Medicare has two big recurring windows with confusingly similar names. The Annual Enrollment Period — October 15 to December 7 — is the broad one, when nearly any coverage change is allowed. The Medicare Advantage Open Enrollment Period — January 1 to March 31 — is narrower: a second chance specifically for people already in an Advantage plan. Knowing which powers belong to which window is the whole game, because the change you can make in one is often impossible in the other.
How to think about this
Think of AEP as the season for decisions and MA-OEP as the season for corrections. In the fall, plans publish next year's networks, formularies and benefits — AEP exists so you can re-decide with that information, whatever coverage you hold. The winter window exists because some Advantage choices only reveal their problems in use: a doctor turns out to be out of network in January, a drug tier surprises you at the pharmacy. If you are in an Advantage plan and the new year disappoints, MA-OEP lets you switch plans or return to Original Medicare once. If you are on Original Medicare and want to change drug plans in February — that power does not exist in this window, and planning as though it does is the classic mistake.
At a glance
| What changes | Annual Enrollment (Oct 15 – Dec 7) | MA Open Enrollment (Jan 1 – Mar 31) |
|---|---|---|
| Who can use it | Everyone with Medicare, whatever coverage they hold. | Only people already enrolled in a Medicare Advantage plan. |
| Switching between Advantage plans | Allowed. | Allowed — once during the window. |
| Leaving Advantage for Original Medicare | Allowed, with a Part D plan added alongside. | Allowed — and you may add a Part D plan as you go. |
| Joining Advantage from Original Medicare | Allowed. | Not allowed. This window only moves you out of or between Advantage plans. |
| Changing standalone Part D plans on Original Medicare | Allowed. | Not allowed for people on Original Medicare. |
| When changes take effect | January 1 of the coming year. | The first of the month after the plan receives your request. |
Annual Enrollment (Oct 15 – Dec 7)
- You want to make a considered change for next year with the new plan details in hand.
- You are on Original Medicare and want a different Part D plan — this is your one regular window.
- You want to move from Original Medicare into an Advantage plan.
MA Open Enrollment (Jan 1 – Mar 31)
- Your new Advantage plan disappointed you in actual use — networks, drugs, or service.
- You joined an Advantage plan in the fall and January revealed something the brochure did not.
- You want out of Advantage and back to Original Medicare early in the year.
Watch out for
- The winter window cannot move you INTO an Advantage plan or between Part D plans on Original Medicare. People plan a February change assuming symmetrical rules and discover the door only swings one way. Check which side of the door you are on before counting on this window.
- Leaving Advantage in winter returns you to Original Medicare — but not necessarily to a Medigap policy. Outside your one-time Medigap open enrollment, buying a supplement may involve health questions, and whether an insurer can decline you varies by state. The exit is guaranteed; the landing is not.
- Fall changes overwrite each other; the winter change happens once. During AEP your last submitted choice wins, so you can revise. In MA-OEP you get a single switch — treat it as one bullet, not a season of browsing.
- The fall Advantage marketing wave peaks precisely because AEP is when everyone can move. A plan that must be decided tonight is a sales tactic, not a deadline — the window is seven weeks long.
Common questions
- I missed AEP. Can I still change my coverage?
- If you are in an Advantage plan, the winter window gives you one switch or an exit to Original Medicare. If you are on Original Medicare, your options before next fall narrow to special enrollment periods triggered by life events — moving, losing other coverage, and similar.
- Do these windows have anything to do with turning 65?
- No. Your initial enrollment period around your 65th birthday is its own thing. AEP and MA-OEP are the recurring annual windows that exist after you are already in the system.
- Can I use the winter window twice if I regret the first switch?
- No — one change per winter. If the second plan also disappoints, you generally wait for the fall. That is exactly why the winter switch deserves more care than the marketing around it suggests.
- Is there an open enrollment for Medigap every year too?
- No, and this surprises many people. Your guaranteed-issue Medigap window happens once, around when Part B begins. A few states add recurring rights, but there is no national annual Medigap open enrollment — which is why the Advantage-to-Medigap path deserves state-specific advice.