Medicare Annual Enrollment Period: 2026 Deadline and What You Need to Know

This article is for general educational purposes only and is not insurance or medical advice. We are not affiliated with the U.S. government or Medicare. For official information, visit Medicare.gov or call 1-800-MEDICARE. See our Medical & Financial Disclaimer for details.

Every fall, mailboxes fill up with Medicare Advantage commercials and reminders to “review your options before it’s too late.” Somewhere in that flood of marketing is a real, hard deadline that actually matters: the Medicare Annual Enrollment Period. Here’s exactly when it runs, what you can change, what it quietly does not let you undo, and how to avoid the mistakes that are expensive precisely because they look reversible.

The Quick Answer

• The next Annual Enrollment Period (AEP) runs October 15 – December 7, 2026
• Any changes you make take effect January 1, 2027
• This is your main annual opportunity to switch Medicare Advantage plans, switch between Medicare Advantage and Original Medicare, or join, switch, or drop a Part D drug plan
• Missing it generally means waiting a full year for your next chance to make these specific changes, unless you qualify for a Special Enrollment Period

The dates, the December 7 deadline and the January 1 effective date all come from Medicare’s own page on joining a plan.

What You Can Actually Change During AEP

• Switch from Original Medicare to a Medicare Advantage plan
• Switch from Medicare Advantage back to Original Medicare
• Switch from one Medicare Advantage plan to a different one
• Join, switch, or drop a standalone Part D prescription drug plan

You can change your mind, and the clock that matters isn’t the one you think

AEP is not a one-shot window. You can submit more than one enrollment request between October 15 and December 7, and only the final one takes effect. CMS enrollment guidance is specific about how “final” is decided: the last enrollment choice, determined by the plan’s receipt date, is the one that becomes effective. The rule appears in the CMS CY 2026 Medicare Advantage and Part D enrollment and disenrollment guidance.

Read that twice, because it changes how you should treat the deadline. December 7 is not the date you have to send something. It’s the date the plan has to have it. A form mailed on December 5 that arrives December 9 is not a late change — it’s no change at all. Medicare makes the same point about the AEP deadline in general terms: the plan must get your enrollment request by December 7.

That’s also why enrolling online or by phone in the last week is safer than mailing a form. Nothing about the calendar changes; what changes is whether the receipt date is instant or up to the postal service.

What AEP Does NOT Cover

• Medigap (Medicare Supplement) enrollment. Medigap has its own one-time, 6-month Open Enrollment Period that starts the first day of the month you are both 65 or older and enrolled in Part B, according to Medicare’s page on when you can buy a Medigap policy. AEP does nothing to reopen it. This has a consequence most people don’t see coming, and it has its own section below.
• First-time Medicare enrollment. If you’re new to Medicare, you enroll during your Initial Enrollment Period, a 7-month window centered on your 65th birthday — not AEP.

The Expensive Mistake: Leaving Medicare Advantage Does Not Get You a Medigap Policy

This is the single most costly thing people do during AEP, and it happens because the window makes the switch look symmetrical. It isn’t.

AEP genuinely does let you drop a Medicare Advantage plan and go back to Original Medicare. What it does not do is guarantee that any insurer will sell you a Medigap policy to sit alongside it. And Original Medicare without Medigap has no annual out-of-pocket maximum at all — which is usually the exact protection the person was trying to get back.

Medicare’s guide to choosing a Medigap policy lists the situations that give you a guaranteed right to buy one. Two of them are “trial rights”, and both are narrow:

• You joined a Medicare Advantage plan (or PACE) when you were first eligible for Medicare at 65, and within that first year you decide you want to switch to Original Medicare. You can then buy any Medigap policy sold in your state.
• You dropped a Medigap policy to join a Medicare Advantage plan for the first time, you’ve been in the plan less than a year, and you want the Medigap policy back.

Notice what both have in common: a 12-month clock, and a first time. Someone who has been in a Medicare Advantage plan for four years and drops it during AEP fits neither. That guide lists no guaranteed issue right for that situation, which means in most states the insurer can put the application through medical underwriting and decline it.

A handful of states give residents broader rights than federal law requires, so state rules are worth checking — but the safe assumption is the federal floor, not the exception.

What to do about it, in order: if you are thinking of leaving Medicare Advantage for Original Medicare plus Medigap, apply for the Medigap policy first and get a written acceptance before you submit the disenrollment. Doing it the other way around means you can end up having successfully left the plan and been refused the replacement, with January 1 arriving either way. If you’ve been in Medicare Advantage more than a year and you’re outside a trial right, treat a Medigap policy as something you have to qualify for, not something AEP hands you.

How to Prepare Before October 15

1. Read your Annual Notice of Change (ANOC) letter. Your plan sends it in September, and it sets out the changes to coverage and costs that take effect in January. Medicare’s page on upcoming plan changes is blunt about what to do with it: review the changes to decide whether the plan will still meet your needs next year — and if you didn’t get it, contact your plan. That last instruction matters more than it sounds. The ANOC is the only document that tells you what your own plan is about to become, and a plan that changed while you weren’t looking is the most common way people end up with the wrong coverage without ever making a decision.
2. Start comparing in October, not December. Since what counts is the plan’s receipt date, every day you leave at the end of the window is a day of margin you’re giving away.
3. Check your specific doctors and medications against any new plan you’re considering — not just the premium or the star rating. A plan can keep its premium identical and still drop your cardiologist or move your drug to a higher tier.
4. If Medigap is part of your plan, start there — see the section above. That application has to succeed before the rest of the sequence makes sense.
5. Mark both dates: October 15 when the window opens, December 7 as a receipt deadline rather than a postmark deadline.

Common Mistakes to Avoid

• Treating December 7 as a postmark deadline. It isn’t. The plan has to have received the request by then.
• Assuming a mistake can be corrected later through a Special Enrollment Period. SEPs require a specific qualifying event. Medicare’s list of Special Enrollment Periods covers moving, losing other coverage, moving into or out of an institution and similar circumstances. Changing your mind is not on it.
• Not reading the ANOC because you’re not planning to switch. This is backwards. If you’re switching, you’ll compare plans anyway. It’s the people who intend to stay who most need to know what they’re staying in.
• Disenrolling from Medicare Advantage before securing Medigap. Covered above, and the most expensive of the four.

What Happens If You Miss the Deadline

If you don’t make changes by December 7, your current coverage generally rolls over automatically for the following year. Your plan continues — but as whatever the ANOC said it was becoming, not as it was. That’s the distinction people miss: “nothing happens” and “nothing changes” are not the same thing.

If you’re unhappy with your plan after missing AEP, you still have options:

• The Medicare Advantage Open Enrollment Period (January 1 – March 31) gives people already in a Medicare Advantage plan one more chance to switch plans or return to Original Medicare. Note the limit: Medicare’s guide to Medicare Advantage and drug plan enrollment periods states you can only make one change each year during that window — unlike AEP, there is no second attempt.
• A Special Enrollment Period may apply if you experience a qualifying life event — moving, losing employer coverage, or moving in or out of an institution are common examples.
• The 5-Star Special Enrollment Period lets you switch once, between December 8 and November 30, into a 5-star-rated plan if one is available where you live. In many counties, none is.

Outside of these specific situations, you’ll generally need to wait for the next Annual Enrollment Period. And none of them reopens the Medigap door.

Frequently Asked Questions

When exactly does the 2026 Annual Enrollment Period run? October 15 through December 7, 2026. Changes made during this window take effect January 1, 2027.

Can I change my mind after making a selection during AEP? Yes, as many times as you like inside the window. Per CMS, the last enrollment choice — measured by when the plan received it — is the one that takes effect.

Is December 7 the date I have to send my request, or the date it has to arrive? The date it has to arrive. Medicare states the plan must get your enrollment request by December 7, and CMS decides competing requests by plan receipt date. Mailing a form in the final days is the riskiest way to enroll.

If I leave Medicare Advantage during AEP, can I buy a Medigap policy? Not necessarily. Unless you’re inside one of the two 12-month trial rights described above, most states allow insurers to underwrite your application and turn you down. Get the Medigap acceptance in writing before you disenroll.

What if I’m happy with my current plan — do I need to do anything? You don’t have to act, but you should still read the ANOC. Your plan can change its premium, network or drug tiers while your enrollment stays exactly where it is.

What happens if I miss both AEP and the Medicare Advantage Open Enrollment Period? Unless you qualify for a Special Enrollment Period, or a 5-star plan is available in your area, you’ll generally wait until the next Annual Enrollment Period.

Bottom Line

Three things decide whether your AEP goes well, and none of them is finding the cheapest plan.

1. Read the ANOC in September. It’s the only document that tells you what your own coverage is about to become.
2. Treat December 7 as a receipt deadline. Enroll early enough that the plan’s paperwork, not the calendar, is the thing you’re ahead of.
3. If Medigap is the destination, secure it before you leave. AEP lets you out of Medicare Advantage; it doesn’t promise you anywhere to land.

Do those three and the deadline stops being the hard part. The plans actually on sale at your address are listed on the official Medicare Plan Finder; if you would rather talk to a person than read a screen, 1-800-MEDICARE is open every day, and a State Health Insurance Assistance Program counselor will go through the shortlist with you at no cost and with nothing to sell.

Sources

• Joining a plan — Medicare.gov. Source for the October 15 – December 7 dates, the January 1 effective date, the requirement that the plan receive your request by December 7, and the list of changes AEP allows.
• CY 2026 Medicare Advantage and Part D Enrollment and Disenrollment Guidance — Centers for Medicare & Medicaid Services. Source for multiple elections being allowed during AEP and for the last choice, by plan receipt date, being the one that takes effect.
• Plan Annual Notice of Change (ANOC) — Medicare.gov. Source for the ANOC being sent by your plan in September, covering changes effective in January, and for the instruction to contact your plan if it doesn’t arrive.
• Choosing a Medigap Policy: A Guide to Health Insurance for People with Medicare — Medicare.gov. Source for the two 12-month trial rights and for the absence of a guaranteed issue right when a long-term Medicare Advantage enrollee voluntarily disenrolls.
• When can I buy a Medigap policy? — Medicare.gov. Source for the 6-month Medigap Open Enrollment Period beginning the first day of the month you are 65 or older and enrolled in Part B.
• Understanding Medicare Advantage & Medicare Drug Plan Enrollment Periods — Medicare.gov. Source for the one-change limit during the January 1 – March 31 Medicare Advantage Open Enrollment Period.
• Special Enrollment Periods — Medicare.gov. Source for the qualifying life events and for the December 8 – November 30 5-star Special Enrollment Period.

All dates and rules on this page were checked against the sources above on September 15, 2026.

Disclaimer: Enrollment periods, dates, and figures mentioned in this article reflect 2026 guidelines from the Centers for Medicare & Medicaid Services (CMS) and are subject to change. Always confirm current details directly with Medicare.gov, 1-800-MEDICARE, or a licensed agent before making a decision.