Medicare Advantage Open Enrollment Period: what caregivers need to know for 2026-2027

Short answer

The Medicare Advantage Open Enrollment Period runs from January 1 to March 31 each year and is only for people already enrolled in a Medicare Advantage plan on January 1. During this window, a Medicare Advantage enrollee can switch to another Medicare Advantage plan or drop Medicare Advantage and return to Original Medicare. It is different from the Annual Enrollment Period (October 15 to December 7), which is open to everyone with Medicare.

The two enrollment windows caregivers confuse most

Two Medicare enrollment windows share the phrase “Open Enrollment.” They are not the same, and mixing them up is one of the most common reasons caregivers miss a window they meant to use.

Annual Enrollment Period (AEP) runs from October 15 to December 7 each year. This is the window most Medicare-eligible people mean when they say “Medicare Open Enrollment.” Anyone with Medicare can make changes: enroll in Medicare Advantage, switch back to Original Medicare, add or change a Part D prescription drug plan, or switch between Medicare Advantage plans. Coverage changes take effect on January 1 of the following year.

Medicare Advantage Open Enrollment Period (MA-OEP) runs from January 1 to March 31 each year. It is a second-chance window, and it is limited: only people already enrolled in a Medicare Advantage plan on January 1 can use it. During MA-OEP a Medicare Advantage enrollee can either switch to another Medicare Advantage plan or drop Medicare Advantage and return to Original Medicare.

The AEP window is the one most caregivers should plan around. The MA-OEP window is the safety net for people who realized in January that the plan they picked in the fall is not the right fit.

Medicare Advantage Open Enrollment Period: dates, who it’s for, what it does

The Medicare Advantage Open Enrollment Period runs from January 1 to March 31 each year. The dates do not shift year over year and do not depend on the state of residence.

Two conditions decide whether the MA-OEP is available to a particular person on a particular year:

1. The person must be enrolled in a Medicare Advantage plan on January 1 of that year. Someone who is in Original Medicare on January 1 cannot use MA-OEP to switch into Medicare Advantage.
2. The change must be initiated by March 31. A request submitted on April 1 is outside the window.

MA-OEP allows one change per person during the window. If a caregiver helps a loved one switch Medicare Advantage plans on February 3, that person cannot use MA-OEP again on March 15 to switch to a third plan. The window is a second chance, not an unlimited retry.

Coverage takes effect on the first day of the month after the request is received. A request submitted on February 3 typically takes effect March 1. A request submitted March 30 typically takes effect April 1.

What you can — and can’t — change during MA-OEP

The MA-OEP window is narrower than most people expect. What you can and cannot do during MA-OEP:

Two terms come up in what follows: Part D is Medicare’s prescription drug coverage — it can be delivered as a standalone plan alongside Original Medicare, or bundled into a Medicare Advantage plan. Medigap (also called Medicare Supplement insurance) is a separate policy that fills the cost-sharing gaps left by Original Medicare — deductibles, copays, and coinsurance. Medigap is only sold to people on Original Medicare; it cannot be paired with a Medicare Advantage plan.

Allowed during MA-OEP:

• Switch from one Medicare Advantage plan to another Medicare Advantage plan (with or without Part D prescription drug coverage).
• Drop Medicare Advantage and return to Original Medicare. When returning to Original Medicare, the person can also enroll in a standalone Part D prescription drug plan as part of the same MA-OEP action.
• Add prescription drug coverage if the new Medicare Advantage plan includes it and the previous one did not.

Not allowed during MA-OEP:

• Switch from Original Medicare into Medicare Advantage. If a person is in Original Medicare on January 1, MA-OEP is not an option for enrolling into Medicare Advantage — that has to wait for Annual Enrollment or a qualifying Special Enrollment Period.
• Enroll in a Medigap policy with guaranteed-issue rights. Medigap has its own enrollment rules, and outside a person’s Medigap Open Enrollment Period or a specific guaranteed-issue right, medical underwriting typically applies. Dropping Medicare Advantage during MA-OEP does not, by itself, create a Medigap guaranteed-issue right in most states.
• Enroll in a standalone Part D plan without also either switching Medicare Advantage plans or returning to Original Medicare in the same action.

The Medigap point is the one most caregivers underestimate. Someone who drops Medicare Advantage during MA-OEP and returns to Original Medicare can go without Medigap and pay the standard Part B cost-sharing on their own, or they can try to buy Medigap and face medical underwriting in most states. That underwriting can result in higher premiums or a declined application if pre-existing conditions apply. Before dropping Medicare Advantage, it is worth checking whether a Medigap policy is available at all.

When Medicare Advantage OEP is the right window vs Annual Enrollment

The Annual Enrollment Period is the primary window for coverage changes. AEP is open to everyone with Medicare, allows the widest range of changes, and lands coverage on the clean January 1 boundary.

The MA-OEP window becomes the right choice in a narrow set of situations:

• The person picked a Medicare Advantage plan during AEP, saw the first month of coverage in January, and realized the plan does not fit — usually because a doctor is out of network, a medication is not on the formulary, or an unexpected cost-sharing surprise appeared.
• A qualifying event does not apply, so a Special Enrollment Period is not available.
• Waiting until the next AEP means eight or nine months of a bad-fit plan.

In these cases MA-OEP is the second-chance window. Outside these situations, AEP handles most planned changes with less complexity.

Special Enrollment Periods and the events that trigger them

Special Enrollment Periods (SEPs) let a Medicare enrollee make coverage changes outside AEP and MA-OEP when a qualifying event happens. SEPs are the primary path for mid-year changes when neither the annual nor the MA-OEP window applies. Below are the qualifying events caregivers see most often, with a brief on the SEP window each triggers:

1. Moving to a new address outside the plan’s service area. The SEP typically opens the month before the move and lasts two months after. If the plan is not notified in advance, the SEP starts the month of notification and lasts two full months after.
2. Losing or changing employer or union coverage (including retirement). The SEP typically opens the month of the loss and lasts two months after. This includes losing coverage under COBRA.
3. Gaining Medicaid or losing Medicaid eligibility. People eligible for both Medicare and Medicaid (“dual-eligibles”) have their own set of SEP rules that allow more frequent changes.
4. Gaining Extra Help (the Low-Income Subsidy for prescription drugs). This SEP allows changes throughout each quarter of the year for the affected calendar year.
5. A new diagnosis of a qualifying chronic condition that makes the person eligible for a Chronic Condition Special Needs Plan (C-SNP) — for example, chronic heart failure, diabetes, or end-stage renal disease. A qualifying diagnosis opens a SEP to enroll in a matching C-SNP.
6. A provider network change mid-year that removes a provider the person actively sees. Not every provider change triggers an SEP automatically — the plan and CMS have discretion on whether the change qualifies. This one is worth asking the plan about directly, and if the plan says no, how to appeal a Medicare denial explains the escalation path.
7. The Medicare Advantage plan terminates or CMS sanctions it in a way that ends the person’s coverage. CMS opens an SEP for the affected enrollees to switch to another plan.
8. A 5-star Medicare Advantage or Part D plan becomes available in the service area. This uses the 5-star SEP, described in the next section.

The SEP that applies determines the length of the window, the effective date of the change, and which plan types are allowed. If a qualifying event happened, the plan or a patient advocate can help identify the correct SEP.

The 5-star Special Enrollment Period

CMS assigns Medicare Advantage and Part D plans a Star Rating on a 1-to-5 scale each year, updated in advance of the fall AEP. Plans with a 5-star rating are the top performers by CMS’s methodology.

If a 5-star Medicare Advantage plan or 5-star Part D plan is available in the person’s service area, they can use the 5-star Special Enrollment Period to switch into it. The 5-star SEP runs from December 8 (the day after AEP closes) through November 30 of the following year, and it can be used once during that window.

Not every state has 5-star plans available every year. The plans that hold 5-star ratings often serve limited geographic areas. Before counting on this SEP, check whether a 5-star plan is available for the loved one’s ZIP code.

A 4-step walkthrough: figuring out which window applies right now

For caregivers looking at a specific situation right now, the window that applies depends on four questions in order:

Step 1 — Is your loved one currently in Medicare Advantage, or Original Medicare?

If Medicare Advantage: MA-OEP is available during January 1 – March 31 regardless of any triggering event. Move to step 3 to see if an SEP applies instead.

If Original Medicare: MA-OEP is not available. Skip to step 2.

Step 2 — Has a qualifying event happened in the last 60 days?

If yes: a Special Enrollment Period likely applies. Match the event to the SEP list in the previous section.

If no: skip to step 4.

Step 3 — Is a 5-star Medicare Advantage or Part D plan available in the service area?

If yes: the 5-star SEP is available from December 8 to November 30 for that plan.

If no: MA-OEP (for MA enrollees) or waiting for AEP (for anyone) are the remaining options.

Step 4 — If none of the above applies, wait for the Annual Enrollment Period.

AEP runs October 15 through December 7 each year. Coverage takes effect January 1.

This decision walkthrough is a starting point. Some situations combine two windows — for example, someone in Medicare Advantage who moves out of the service area in February can use both MA-OEP and the moving SEP. When windows overlap, the SEP typically offers the cleanest path because it is tied to a specific event rather than a general second chance.

What to check after a mid-year switch

Once a mid-year switch takes effect, five items are worth checking in the first 30 days:

1. Provider list re-verification. The new plan may cover most of the person’s providers, but not necessarily all. Confirm each provider — primary care, specialists, dentist if the plan covers dental — is in-network with the new plan.
2. Formulary re-check. Each Medicare Advantage plan sets its own formulary. Medications that were on the previous plan’s formulary may not be on the new one, or may sit in a different cost-sharing tier. Bring the medication list to the new plan’s website or call the number on the new ID card.
3. ID card timing. New plan ID cards typically arrive within 7-10 business days of the coverage effective date. If a card has not arrived by then, call the plan’s member services line. In the meantime, the plan can confirm coverage over the phone for pharmacies and providers.
4. First bill sanity-check. The first bill under the new plan often surfaces cost-sharing differences the person did not expect. Compare the first month of copays and any deductible activity to the plan’s Summary of Benefits.
5. Continuity of care. Under CMS-4208-F, effective 2026, a new Medicare Advantage plan must honor an active prior-authorization approval for at least 90 days when a person switches plans mid-treatment. If a treatment or medication was previously approved and the new plan is asking for a fresh authorization, that 90-day continuity protection applies — the plan cannot interrupt an active course of treatment mid-transition. For details on how prior authorization rules under CY 2026 work, our Medicare prior authorization guide walks through the timelines.

If any of these five items raises a red flag, address it before the next month’s care begins. Waiting turns a fixable issue into a denied claim.

When it makes sense to work with a patient advocate

Enrollment-window decisions are one of the few Medicare tasks where a small time investment during the right window saves months of the wrong plan. The tradeoff involved — is the current plan bad enough to switch, is there a better option available for this specific person’s providers and medications, is a Medigap policy available if returning to Original Medicare — is exactly the coverage-navigation work a patient advocate does. Baba works with families to compare a loved one’s specific providers and prescriptions against the available plans in their ZIP code and identify the option that fits before the window closes.

Frequently asked questions

Can I switch Medicare Advantage plans more than once during MA-OEP?

No. MA-OEP allows one change per person during the January 1 – March 31 window. Once a change has been made and the new coverage takes effect, MA-OEP is used for that year.

What happens if I miss MA-OEP?

If none of the Special Enrollment Periods applies, the next window is the Annual Enrollment Period (October 15 – December 7) with coverage changes taking effect January 1 of the following year. That means someone who misses MA-OEP and does not have a qualifying event will typically stay on the current Medicare Advantage plan for at least the remaining calendar year.

Is MA-OEP the same as the Annual Enrollment Period?

No. Annual Enrollment (AEP) runs October 15 – December 7 and is open to everyone with Medicare. MA-OEP runs January 1 – March 31 and is only for people already enrolled in a Medicare Advantage plan on January 1. AEP allows a wider range of changes; MA-OEP is a narrower second-chance window.

Can I add Medigap during MA-OEP?

MA-OEP itself does not create a Medigap guaranteed-issue right in most states. Someone who drops Medicare Advantage during MA-OEP and returns to Original Medicare can apply for Medigap, but the application will typically go through medical underwriting outside a person’s own Medigap Open Enrollment Period. That underwriting can result in higher premiums or a declined application. Check Medigap availability before dropping Medicare Advantage.

What if my plan is terminating — do I get a Special Enrollment Period?

Yes. If a Medicare Advantage plan terminates or is sanctioned by CMS in a way that ends coverage, CMS opens a Special Enrollment Period for the affected enrollees to switch to another plan. The SEP typically starts two months before the termination and lasts one month after. Plans are required to send written notification to affected enrollees explaining the SEP and the deadline.

The information on this page is provided for general educational purposes only. It is not medical, legal, or financial advice and does not replace the guidance of a qualified professional. Medicare rules and enrollment windows can change from year to year and the specifics for a particular situation depend on the plan, the state, and the individual’s circumstances. If you have questions about your own or a loved one’s Medicare enrollment options, consult the resources at medicare.gov, contact your plan directly, or speak with a licensed insurance advisor or patient advocate.