Dates, deadlines, and the rules behind them
There are five ways into or out of a Medicare Advantage plan, and each one allows different changes. This page lays out every window, the exact 2026 and 2027 dates, and what you can and cannot do inside each one.
Medicare is not an open market you can shop any day of the year. Outside of a qualifying life event, there are exactly two general opportunities to change a Medicare Advantage plan, and they allow different things. Learning which one you are in saves an enormous amount of frustration.
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| Window | When | Who it is for | What you can do | Coverage starts |
|---|---|---|---|---|
| Initial Enrollment Period | 7 months around your 65th birthday | People newly eligible for Medicare | Enroll in Part A and Part B, then join a Medicare Advantage or Part D plan | Usually the month you turn 65, or later if you enroll after your birthday month |
| Annual Enrollment Period (AEP) | October 15 to December 7 every year | Everyone with Medicare | Join, switch, or drop a Medicare Advantage plan; join, switch, or drop a Part D plan; move between Original Medicare and Medicare Advantage | January 1 |
| Medicare Advantage Open Enrollment (MA OEP) | January 1 to March 31 every year | Only people already in a Medicare Advantage plan on January 1 | One change: switch to a different Medicare Advantage plan, or return to Original Medicare and add a Part D plan | First of the month after the plan receives your request |
| Special Enrollment Period (SEP) | Triggered by a qualifying event | People who move, lose coverage, or meet other criteria | Varies by the event that triggered it | Usually the first of the following month |
| General Enrollment Period (GEP) | January 1 to March 31 every year | People who missed signing up for Part B | Enroll in Part B, then use a related window to join a Medicare Advantage or Part D plan | The first of the month after you enroll |
Dates and rules from Medicare.gov. Late enrollment penalties may apply if you delay Part B or Part D without other creditable coverage.
Mark these dates
The autumn cycle for 2027 coverage is already underway. Here is what happens and when.
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| Date | What happens | What you should do |
|---|---|---|
| By September 30, 2026 | Your plan mails the Annual Notice of Change (ANOC) for 2027 | Read it. It lists every change to your premium, copays, deductible, drug formulary, and network. This is the single most important piece of mail you get all year. |
| Around October 1, 2026 | Medicare Plan Finder is updated with 2027 plan data | You can look at next year's plans, but you cannot enroll yet. |
| October 15, 2026 | Annual Enrollment Period opens | Enrollment requests can now be submitted for 2027 coverage. |
| December 7, 2026 | Annual Enrollment Period closes | Last day to make a change for January. If you submit several changes, only the last one counts. |
| January 1, 2027 | New coverage begins | Carry your new card. Confirm your pharmacy and your first appointment go through as expected. |
| January 1 to March 31, 2027 | Medicare Advantage Open Enrollment | If January shows you the plan was wrong, you get one correction here. |
A note on 2027: CMS finalized its Contract Year 2027 rules for Medicare Advantage and Part D in April 2026, including changes to supplemental benefits and Star Ratings, with marketing and communications provisions taking effect October 1, 2026. Plans build their 2027 benefits around those rules, which is a good reason to read your Annual Notice of Change carefully this September rather than assuming your plan carried over unchanged.
Your Initial Enrollment Period runs for seven months: the three months before the month you turn 65, your birthday month, and the three months after. If your birthday falls on the first of a month, the whole window shifts one month earlier.
Once you have both Part A and Part B, you can use this same window to join a Medicare Advantage plan. Enrolling in the three months before your birthday month generally gives you coverage starting the first day of your birthday month. Waiting until after your birthday month delays the start date.
The Initial Enrollment Period runs February 1 through August 31, 2027. Enrolling in February, March, or April means coverage starts May 1. Enrolling in May, June, July, or August means coverage starts the first of the month after you sign up, so a July enrollment starts August 1 and leaves you uncovered in May, June, and July.
If you are still working past 65 and covered by an employer group plan with 20 or more employees, different rules apply and delaying Part B may be the right call. That decision is worth a conversation before you make it, because getting it wrong creates a permanent Part B penalty of 10% for each full 12-month period you could have had Part B and did not.
This is the broadest window. Everyone with Medicare can use it, no qualifying event is needed, and almost any change is allowed.
Doing nothing is a valid choice. If your plan still exists in 2027 and you take no action, your enrollment continues automatically. Doing nothing without reading the Annual Notice of Change is a different thing, and it is how people end up surprised in February.
The Medicare Advantage Open Enrollment Period runs January 1 through March 31. It exists as a correction mechanism: you have started using the plan, something is wrong, and you get one chance to fix it.
It is narrower than Annual Enrollment in three ways that catch people out.
The change takes effect the first of the month after the plan receives your request, so a February 20 request generally starts March 1.
A Special Enrollment Period is triggered by a life event. There is no single SEP with one set of rules. Each trigger has its own window and its own list of allowed changes, and this is the area where a licensed agent earns their keep.
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| Event | Typical window | Notes |
|---|---|---|
| You move outside your plan's service area | The month you move plus two more months, or from the month you tell the plan if you tell it in advance | Medicare Advantage plans are sold county by county. Tell the plan before you move to start the window earlier. |
| You move within the area but new plans become available | Same as above | Worth checking. Availability can change across a county line. |
| You lose employer or union coverage | Generally two months after coverage ends | Keep the letter documenting the end date. You will be asked for it. |
| Your plan leaves Medicare or stops serving your county | Announced by the plan, usually running into the following year | The plan must notify you. Do not wait until January to act. |
| You move into, live in, or leave a nursing home or long-term care facility | Ongoing while you live there, plus two months after you leave | One of the few SEPs you can use repeatedly. |
| You qualify for Medicaid or for Extra Help | Depends on your exact status | CMS restructured these opportunities in 2025. There is now a monthly opportunity to join an integrated dual eligible plan and a separate quarterly opportunity for stand-alone drug plans. Which applies depends on your circumstances, so ask before assuming. |
| You qualify for a Special Needs Plan | Varies by SNP type | Chronic condition, institutional, and dual eligible plans each have their own rules. See plan types. |
| You want to join a 5-star plan | December 8 through November 30, once per year | Only if a 5-star Medicare Advantage or Part D plan is offered where you live. |
| A federally declared disaster or emergency | Set by CMS for the affected area | Lets you make a change you missed because of the emergency. |
| You leave incarceration or return to the United States | Set by the circumstance | Documentation is usually required. |
This table covers the events we see most often. It is not the complete federal list, and the exact window for your situation depends on details such as when you notified the plan. Call us or 1-800-MEDICARE to confirm before you rely on one.
Leaving a Medicare Advantage plan during Annual Enrollment or the January window is easy. Getting a Medicare Supplement policy to go with Original Medicare afterwards may not be, and this is the part of the system people most often learn about too late.
Outside of certain protected windows, most states let a Medigap insurer review your health history and decline you or charge you more. Two protections matter most.
If you joined a Medicare Advantage plan when you first became eligible at 65, you generally have a guaranteed right to leave for Original Medicare and buy a Medigap policy within your first 12 months. Separately, if you dropped a Medigap policy to try Medicare Advantage for the first time and want to switch back within 12 months, you generally have a right to get that policy back if it is still sold.
After those 12 months pass, in most states you are subject to medical underwriting. A few states have broader rules. Ask us which applies where you live.
None of this makes Medicare Advantage the wrong choice. It does mean the decision deserves more thought in year one than in later years, because year one is when the door back is widest open. We walk through both directions on the Medicare Supplement page and the costs page.
Find your situation on the left. Today is in August, so the third column tells you whether you can act now or need to wait.
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| I want to | Window that allows it | Next opportunity |
|---|---|---|
| Switch from one Medicare Advantage plan to another | Annual Enrollment, or the January window if I am already in a plan, or a qualifying SEP | October 15, 2026 for a January 1, 2027 start |
| Join Medicare Advantage from Original Medicare | Annual Enrollment, or a qualifying SEP | October 15, 2026 |
| Leave Medicare Advantage for Original Medicare | Annual Enrollment, or the January window, or a qualifying SEP | October 15, 2026, or January 1, 2027 |
| Add a stand-alone Part D plan | Annual Enrollment, or the January window only if I am also leaving Medicare Advantage | October 15, 2026 |
| Change plans because I am moving in September | Special Enrollment Period for a permanent move | Now. Tell your plan before you move to start the window earlier |
| Enroll because I turn 65 in November | Initial Enrollment Period | Your window opened August 1 for a November 1 start |
| Sign up for Part B because I missed it | General Enrollment Period | January 1, 2027 |
October 15 through December 7, 2026. Changes you make in that window take effect January 1, 2027.
No, and confusing the two is common. The Marketplace window for 2027 coverage runs from November 1, 2026 into January 2027 in most states. Medicare Annual Enrollment ends December 7. If you have Medicare, December 7 is your deadline.
Only with a Special Enrollment Period. Moving, losing employer coverage, entering a nursing home, qualifying for Medicaid, and a plan leaving your county are the most common triggers. Without one of those, the next general opportunity is October 15.
As many times as you like between October 15 and December 7. Only the last change on file before the deadline takes effect.
No. Enrolling in a new Medicare Advantage or Part D plan automatically disenrolls you from the old one. Cancelling separately can create a coverage gap, so do not do it.
No. You return to Original Medicare Part A and Part B. You will want to consider a Part D drug plan and, if you qualify, a Medicare Supplement policy at the same time.
The plan must notify you, and you get a Special Enrollment Period to choose something else. If you do nothing, you may be moved to Original Medicare without drug coverage, which starts a Part D penalty clock. Act on that letter.
If you go 63 days or more without Part D or other creditable drug coverage after your Initial Enrollment Period, Medicare adds roughly 1% of the national base beneficiary premium for each uncovered month, and the surcharge is permanent.
Official resource
Medicare.gov publishes the official enrollment rules and your State Health Insurance Assistance Program offers free unbiased counseling. A licensed agent can compare the specific plans available in your county. Agents do not provide medical, legal, or official eligibility advice.
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