Updated July 2026 · Reviewed by the CoverageCo team
Medicare's Annual Enrollment Period runs October 15 through December 7 each year, and changes you make take effect January 1. During it you can join, switch, or drop a Medicare Advantage plan or a Part D prescription plan. It is not, however, a guaranteed window to buy a Medigap policy.
Key takeaways
- October 15 – December 7, with changes effective January 1.
- You can change Advantage and Part D plans freely during this window.
- Medigap is different — it generally still requires medical underwriting outside your one-time window.
- Staying put is a decision too, because plans change their formularies and networks every year.
What you can actually do during AEP
The Annual Enrollment Period is the broadest window most people get each year:
- Join a Medicare Advantage plan, or switch from one Advantage plan to another.
- Drop an Advantage plan and return to Original Medicare.
- Join a standalone Part D prescription drug plan, switch plans, or drop coverage.
What AEP does not do
This is the part that trips people up, and it's worth being blunt about.
AEP is not a guaranteed-issue window for Medigap. If you want to add a Medicare Supplement policy during the fall, most states still allow the insurer to review your health and decline you — unless you're inside your one-time Medigap open enrollment period or qualify for a specific guaranteed-issue right.
People routinely assume the fall window covers everything Medicare-related. It doesn't. If Medigap is part of your plan, the timing that matters is when you first enrolled in Part B, not October.
Why reviewing matters even if you're happy
Plans change every year. Formularies get reshuffled, tiers move, provider networks shift, and premiums adjust.
Your plan is required to send you an annual notice describing what's changing for the coming year. It arrives in early fall, and it looks exactly like the junk mail everyone throws away.
The practical consequence: a plan that fit you perfectly can quietly stop covering a medication you depend on, and you find out at the pharmacy counter in January. Choosing to stay is fine — choosing without looking is what costs money.
The other windows, so you're not confused
Several Medicare windows exist and they're easy to mix up:
| Window | When | What it's for |
|---|---|---|
| Initial Enrollment Period | 7 months around your 65th birthday | First-time enrollment |
| Annual Enrollment Period | Oct 15 – Dec 7 | Change Advantage or Part D for next year |
| Medicare Advantage OEP | Jan 1 – Mar 31 | One change if you're already in an Advantage plan |
| Special Enrollment Periods | Varies | Triggered by events like moving or losing coverage |
How to use the window well
Start with your medication list, your doctors, and your pharmacy. Compare only plans that clear all three, then look at cost. That order matters more than any other advice on this page.
Give yourself time. Waiting until the first week of December means rushing a decision you'll live with for a full year, and agents are at their busiest then.
A licensed agent can run your specific drugs and providers against the plans available where you live, at no cost to you. If your current plan still wins, that's a good outcome you can act on with confidence.
Common questions
When is Medicare's Annual Enrollment Period?
October 15 through December 7 each year. Changes you make take effect January 1. Confirm current dates at Medicare.gov, since they're set by CMS.
Can I buy a Medigap policy during AEP?
Not with guaranteed acceptance. AEP covers Medicare Advantage and Part D changes. Medigap generally requires medical underwriting outside your one-time six-month Medigap open enrollment period or a specific guaranteed-issue situation.
What's the difference between AEP and Medicare Advantage Open Enrollment?
AEP runs October 15 to December 7 and is open to everyone on Medicare. Medicare Advantage Open Enrollment runs January 1 to March 31 and is only for people already enrolled in an Advantage plan, allowing one change.
What happens if I do nothing during AEP?
Your current coverage generally continues into the next year with whatever changes the plan has made to its formulary, network, and costs. That's why reviewing the annual notice matters even if you intend to stay.