Quick answer: The Medicare Advantage Open Enrollment Period (sometimes called MA OEP) runs January 1 through March 31 each year. Medicare.gov says it is available if you are already in a Medicare Advantage Plan. During that window you may make one change: switch to a different Medicare Advantage Plan (with or without drug coverage), or drop Medicare Advantage and return to Original Medicare. If you return to Original Medicare, you can also join a stand-alone Medicare drug plan. Coverage starts the first day of the month after the plan gets your request. You cannot use this period to move from Original Medicare into a Medicare Advantage Plan, or to switch stand-alone drug plans if you are already in Original Medicare. That broader set of moves belongs to the fall Open Enrollment Period, October 15–December 7, which is covered in our Medicare Annual Enrollment Period checklist. This explainer sits in our Medicare guide.
Sources: Medicare.gov, “Joining a plan” and “Remember Key Medicare Dates”; CMS publication “Understanding Medicare Advantage and Medicare Drug Plan Enrollment Periods” (MA OEP is January 1–March 31; one change; effective the first of the month after the plan receives the request; people in Original Medicare cannot use OEP to join an Advantage plan or switch stand-alone drug plans). Fall Open Enrollment remains October 15–December 7, with most of those changes starting January 1. Checked November 2026. This is general consumer information, not legal, tax, medical or benefits advice. Medicare rules, plan designs and dollar amounts change. Confirm current details on Medicare.gov, with CMS, Social Security, your plan, and a State Health Insurance Assistance Program (SHIP) counselor before you rely on a figure or a deadline.
How This Period Differs From Fall Open Enrollment
Two yearly windows get similar names and do very different jobs. The fall Open Enrollment Period, October 15 through December 7, is the time when people with Medicare can make a wide range of plan changes for the following calendar year, whether they have Original Medicare or Medicare Advantage. Those fall changes generally start on January 1 if the plan has your request by December 7.
The Medicare Advantage Open Enrollment Period is narrower and later. It runs January 1 through March 31, and Medicare.gov describes it as available only if you are already in a Medicare Advantage Plan (or, in a related early-Medicare window, within the first three months you have Medicare after joining an Advantage plan during your Initial Enrollment Period). The point of the winter window is a second chance if the Advantage plan you have in January is not working — a network surprise, a drug-list problem, or a plan you want to leave.
If you are in Original Medicare in January, this winter window is not your path into an Advantage plan. You generally wait for fall Open Enrollment, or for a Special Enrollment Period if a qualifying life event applies, such as a move. Mixing up the two calendars is a common way people miss a deadline or assume a change they cannot make.
Changes made during the Advantage Open Enrollment Period start sooner than fall changes. Official materials say new coverage begins the first day of the month after the plan gets your enrollment or disenrollment request. A request the plan receives in January can start February 1; a March request can start April 1, depending on when it is received. Do not assume a verbal call on March 31 is complete until the plan has the request in the way it requires.
You can make only one change during this period. Use it deliberately. A second switch generally has to wait for another legal window.
What You Can Do, and What You Cannot
If you are already in a Medicare Advantage Plan, official CMS enrollment-period materials say you may:
- Switch to another Medicare Advantage Plan, with or without drug coverage.
- Disenroll from your Medicare Advantage Plan and return to Original Medicare. If you do that, you can join a stand-alone Medicare drug plan.
You cannot, during this same winter window, switch from Original Medicare to a Medicare Advantage Plan, join a drug plan if you are in Original Medicare and not coming from Advantage, or switch one stand-alone Part D plan for another while in Original Medicare. Those limits matter if a family member in Original Medicare is trying to use “open enrollment” in February.
Returning to Original Medicare is not only a plan paperwork step. You will again use providers who accept Original Medicare, you will want to think about Medigap (which is sold only with Original Medicare, not alongside Advantage), and you will need a drug plan if you want Part D coverage and do not already have creditable drug coverage. Medigap is not automatic. Whether a company must sell you a policy depends on guaranteed issue rights, a trial right, or your Medigap Open Enrollment Period, which our Medigap materials and Medicare.gov explain. If you do not have one of those protections, a company may use medical underwriting. That is a reason to call a SHIP counselor before you drop a plan.
If you switch from one Advantage plan to another, confirm the new plan’s provider network, drug list, prior authorization rules, and costs on Medicare.gov’s plan comparison tool, and confirm that the plan has your request. Keep records of the confirmation. Until the new plan starts, follow the plan you still have.
People who joined an Advantage plan during their Initial Enrollment Period also have a short early window — official materials describe a chance, within the first three months you have Medicare, to change to another Advantage plan or go back to Original Medicare. That is related to, but not identical with, the calendar OEP. If you are new to Medicare, read Medicare.gov’s enrollment-period pages or use our Initial Enrollment Period guide rather than guessing which clock applies.
How to Use the Window Without Creating a Gap
Start with the official comparison, not a sales call. Medicare.gov and 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048) are the federal starting points. A SHIP counselor can walk through the same options at no cost. If you use a broker or plan representative, you still own the deadline and the confirmation.
If you will need a stand-alone drug plan after leaving Advantage, join it as part of the same official process so you are not left without creditable drug coverage. Official materials have long warned that going 63 days or more without creditable drug coverage can trigger a Part D late enrollment penalty, a topic also covered in our late enrollment penalties article. Do not assume hospital or employer leftovers are creditable without checking.
If you want Medigap after you return to Original Medicare, start that conversation before you disenroll, using Medicare.gov’s guaranteed issue and trial-right explanations and your state insurance department. A winter plan change that is allowed under OEP can still leave you without a supplement if you are outside a protection window.
Write down the plan name, the date you submitted the request, and any confirmation number. Check your Medicare.gov account or wait for official notices. If something does not appear after a reasonable time, call the plan and 1-800-MEDICARE rather than assuming it failed or succeeded.
Do not drop a current plan on a verbal promise that “we will get you in.” Official enrollment through Medicare or the plan is what starts the clock. After the change takes effect, review the first Explanation of Benefits or claims carefully.
If you are happy with your Advantage plan in January, you do not have to do anything during OEP. The window is a right, not an assignment.
A last practical point: fall Open Enrollment decisions start in January. If you already used the fall window to join a new Advantage plan effective January 1, OEP is still available for one additional change if that new plan is a poor fit. Use official dates, not marketing mail that blurs “open enrollment” across the whole winter.
Timing Traps, Notices and Who Can Help
Sales mail often prints “open enrollment” in January as if every kind of Medicare change were still available. Official calendars are stricter than that language. A person already in a Medicare Advantage Plan has the winter window described above. A person in Original Medicare does not get a general mid-winter path into Advantage. Relatives who share a household can be on different clocks at the same time, which is why each enrollment request should be checked against that person’s current coverage, not against a shared family rumor.
Plan Annual Notices of Change, which arrive in the fall, still matter in January. The benefits that started on January 1 are the benefits you are testing during this window. When a network doctor, a formulary drug, or a premium is not what you expected, official comparison tools for the current year — not last year’s brochure — are the documents to use. Write down the mismatch, then decide whether the one allowed winter change is worth using.
SHIP counselors, 1-800-MEDICARE, and the Medicare.gov account are the official help desk for this decision. A licensed agent can also submit a request, but the confirmation should still show up in official channels. If two requests are submitted close together, official processing can produce a result you did not intend, because the period allows one change. Stop and verify before a second form goes in.
People who qualify for Extra Help or a Medicare Savings Program should mention that status when they compare, because cost-sharing and premium assistance can change the math of a plan switch. Official eligibility and applications remain on Medicare.gov. Losing a low-income subsidy can also create other official special enrollment rights; those rights are separate from the January–March Advantage window and should be read on the Special Enrollment Periods page rather than assumed.
Keep a one-page record each winter: current plan name, confirmation number if you change, the effective date, and a note about Medigap or drug coverage if you returned to Original Medicare. That page is what a caregiver, a pharmacist, or a later appeals reviewer will need if a claim is billed under the wrong plan in April.
Frequently Asked Questions
Can I use the January–March window if I have only Original Medicare?
No. Medicare.gov describes this period as available if you are already in a Medicare Advantage Plan. Original Medicare plan changes in the winter generally require a Special Enrollment Period or waiting until fall Open Enrollment.
How many times can I switch between January 1 and March 31?
Official CMS materials say you can make one change during this period.
When does the new coverage start?
The first day of the month after the plan gets your request, according to Medicare.gov and CMS enrollment-period publications.
If I go back to Original Medicare, do I automatically get a Medigap policy?
No. Medigap is a separate purchase. You may have a guaranteed issue right or a trial right in some situations; otherwise a company may be able to use health underwriting. Check Medicare.gov and your state insurance department.
Can I join a stand-alone drug plan during OEP?
Yes if you are leaving Medicare Advantage and returning to Original Medicare, according to official enrollment-period materials. If you already have only Original Medicare, this winter window is not the general time to join or switch a stand-alone drug plan.
Is this the same as the October 15–December 7 period?
No. Fall Open Enrollment is broader and usually starts coverage the next January 1. The Advantage Open Enrollment Period is a narrower winter window with a one-change limit and a mid-year start date.
