Quick Answer: The Medicare Annual Enrollment Period (AEP) runs October 15 through December 7 every year. During this window, you can switch Medicare Advantage plans, switch Part D prescription drug plans, move from Original Medicare to Medicare Advantage, or move from Medicare Advantage back to Original Medicare. Changes made during AEP take effect January 1 of the following year.
| Window | October 15 – December 7, 2026 |
| Coverage effective | January 1, 2027 |
| Who it's for | Anyone already enrolled in Medicare who wants to change plans |
| What you can change | Medicare Advantage plan, Part D plan, or switch between Original Medicare and Medicare Advantage |
| Number of changes allowed | Unlimited during the window — your last choice by Dec 7 is what takes effect |
| If you miss it | You're generally locked into your current plan until the next AEP, unless you qualify for a Special Enrollment Period |
The Annual Enrollment Period, sometimes called Fall Open Enrollment, is the one guaranteed window every year when anyone already on Medicare can change their coverage without answering health questions. It runs October 15 through December 7, and any changes you make take effect January 1 of the following year.
Note that AEP does not let you newly enroll in a Medicare Supplement (Medigap) policy without underwriting — Medigap has its own separate rules, generally tied to your Medicare Part B start date.
Even if you’re happy with your current plan, it’s worth reviewing every AEP. Medicare Advantage and Part D plans can change their premiums, drug formularies, provider networks, and extra benefits from year to year, sometimes significantly. A plan that fit well last year may have dropped a medication from its formulary or lost a doctor from its network for the coming year, and you won’t necessarily be notified in a way you’ll notice.
AEP is a lot to review on your own every year. We check your current Medicare Advantage or Part D plan against what else is available in your area, flag any network or formulary changes, and handle the enrollment paperwork, at no cost to you.
The Medicare Annual Enrollment Period runs October 15 through December 7, 2026. Changes made during this window take effect January 1, 2027.
AEP (Oct 15-Dec 7) is open to all Medicare beneficiaries and allows broad changes, including switching between Original Medicare and Medicare Advantage. The Medicare Advantage Open Enrollment Period (Jan 1-Mar 31) is only for people already in a Medicare Advantage plan and allows one plan switch.
Yes. You can make as many changes as you want between October 15 and December 7 — only your last selection before the deadline actually takes effect on January 1.
If you take no action, you generally stay on your current Medicare Advantage or Part D plan for the following year, even if its costs, network, or formulary have changed. That’s why reviewing the Annual Notice of Change each year matters.
AEP itself doesn’t guarantee Medigap enrollment without underwriting. Medigap has separate enrollment rules generally tied to when you first enrolled in Medicare Part B, though it’s still worth asking about your options.