The Annual Enrollment Period (AEP) runs October 15 through December 7 each year. During this window, people who are already enrolled in Medicare can switch plans, change their drug coverage, or move between Medicare Advantage and Original Medicare. This is not a window for people enrolling in Medicare for the first time — it is for existing beneficiaries who want to make a change.
Any changes you make during AEP take effect January 1 of the following year. If you miss the December 7 deadline, your current plan renews automatically and you generally cannot make changes until the next AEP — a full year away.
What You Can Change During AEP
During the Annual Enrollment Period, existing Medicare beneficiaries can make the following changes:
- Switch from one Medicare Advantage plan to another — If your current plan raised premiums, dropped a doctor from its network, or changed what drugs it covers, AEP is when you move to a different Advantage plan in your area. New coverage begins January 1.
- Switch from Medicare Advantage back to Original Medicare — If you want broader provider access, fewer network restrictions, or your health needs have changed, AEP is the window to return to Original Medicare. You can also add a standalone Part D drug plan at the same time. Important: returning to Original Medicare does not automatically give you a Medigap policy — see the “What You Cannot Change” section below for why this matters.
- Switch from Original Medicare to Medicare Advantage — If you are currently on Original Medicare and want to try a Medicare Advantage plan — for added benefits like dental, vision, or hearing coverage, or to cap your out-of-pocket costs — AEP is the enrollment window. Coverage begins January 1.
- Join, switch, or drop a Part D drug plan — If your prescriptions are no longer covered under your current plan’s formulary, your drug costs have increased, or a better plan is available in your area, AEP is when you make that change. See our Part D guide for how Part D works and how to compare plans.
- Drop a Part D plan — If you are gaining creditable drug coverage from another source, you can drop your standalone Part D plan during AEP without penalty.
What You Cannot Change During AEP
The Annual Enrollment Period covers plan switching — it does not open the door to everything. These changes are not possible during AEP:
- Switching Medigap (Medicare Supplement) policies — This is the most common and costly misconception about AEP. The Annual Enrollment Period does not give you the right to change Medigap plans. Medigap has its own open enrollment window — the six months immediately after your Part B begins — during which insurers cannot reject you or charge more based on your health. After that window, in most states, insurers can underwrite based on your health history. AEP does not change this. If you want to switch Medigap plans outside your original open enrollment window, get advice from a Medicare advisor before assuming you can. See our Medicare Advantage vs. Medigap guide for how the two tracks compare.
- Enrolling in Medicare for the first time — AEP is for existing beneficiaries switching plans. If you are enrolling in Medicare for the first time, your Initial Enrollment Period — the seven-month window around your 65th birthday — is the right time to act, not AEP.
- Getting changes effective before January 1 — All AEP changes take effect January 1 of the following year, without exception. If you need coverage to change sooner because of a qualifying life event, a Special Enrollment Period may apply instead.
Why You Should Review Your Plan Every Year
Medicare plans are not locked in permanently. Insurers are allowed to change premiums, deductibles, copays, provider networks, and drug formularies every year. A plan that fit your situation in January may look very different by the following October.
By September 30, your plan is required to send you an Annual Notice of Change (ANOC). This document shows exactly what is changing in your plan for the coming year. Read it as soon as it arrives. Any increase to your premium, change to your network, or drug that has moved to a higher cost tier is a signal to shop during AEP. Doing nothing means your current plan renews automatically — which may be fine, or may cost you significantly more next year.
The right plan for last year may cost you significantly more next year if you do not review during AEP.
⚠️ Medicare enrollment has deadlines — missing them costs you money.
Late enrollment penalties for Medicare Part B and Part D can follow you for life. If you’re approaching 65 or a qualifying life event, don’t wait. Our partner Chapter Medicare offers free, expert guidance on enrollment timing and plan selection.
📞 Call 615-639-1937 | 🔗 askchapter.org/money
Help is ALWAYS FREE. Chapter is compensated by insurance carriers, not by you.
How to Compare Plans Before Making a Change
AEP is not the time to guess. Here is a straightforward approach to comparing options before the window closes:
- Read your Annual Notice of Change first. Identify exactly what is changing in your current plan — premiums, network, drug coverage — before you look at anything else.
- List your doctors, specialists, and prescriptions. These are your comparison criteria. A plan with a low premium that doesn’t cover your medications or include your primary doctor is not a savings — it’s a liability.
- Use medicare.gov/plan-compare. Enter your zip code and prescriptions to see Advantage and Part D plans available in your area. The tool estimates annual costs based on your specific drug list.
- Check total annual costs, not just monthly premiums. Add up premium + deductible + expected copays for a realistic cost comparison. A $0-premium plan can still cost more than a plan with a modest monthly cost if its copays are higher.
- Confirm provider network before switching to an Advantage plan. Call the plan directly or use their online directory to verify your doctors are in-network before you enroll.
For a deeper look at how Medicare Advantage and Original Medicare compare as coverage tracks, see our Medicare Advantage vs. Original Medicare guide.
AEP Checklist
Use this checklist to stay on track before the December 7 deadline:
- Read your Annual Notice of Change when it arrives by September 30. Flag any changes to premium, network, or drug coverage.
- List your current doctors, specialists, and prescriptions. Use these as your comparison criteria for any new plan.
- Visit medicare.gov/plan-compare and run a side-by-side comparison of plans available in your area.
- If you are switching to Original Medicare, understand the Medigap rules before assuming you can get supplemental coverage. The rules are different from AEP.
- Make your selection and enroll before December 7. Do not wait until the final days — processing takes time and the window does not extend.
- After January 1, confirm your new coverage is active by contacting your plan directly.
Missing the December 7 deadline means your current plan renews automatically and you cannot make changes until the next Annual Enrollment Period.
🆓 Don’t navigate enrollment alone — free help is available.
Our partner Chapter Medicare can help you confirm your enrollment window, avoid penalties, and choose the right plan before your deadline.
📞 Call 615-639-1937 | 🔗 askchapter.org/money
ALWAYS FREE. No obligation.
Disclosure: We may receive a referral from Chapter if you choose to use their service. Chapter is a licensed health insurance agency and is not affiliated with or endorsed by Medicare or any government agency.
Related Medicare guides
Medicare Advantage vs. Original Medicare — How the two coverage tracks compare, and which may be right for your situation
Medicare Advantage vs. Medigap — What Medigap covers, how it differs from Advantage, and the Medigap enrollment window rules
Medicare Special Enrollment Periods — When you can make changes outside AEP, and how long each window lasts
Free Medicare Help from Chapter Medicare — What Chapter is, who they help, and what to expect before you call
Medicare Overview — How Medicare is structured, what each part covers, and how to navigate the system