Medicare’s fall open enrollment runs from October 15 to December 7, 2026, and it lets people drop a Medicare Advantage plan and go back to Original Medicare. What the switch does not come with is a promise that a private insurer will sell a Medigap supplement to the person making it.

Medicare.gov says plainly that outside certain protected situations, there is no federal guarantee that an insurance company will sell a Medigap policy. That gap catches people who assume the supplement is waiting for them when they leave.

Why a Medigap sale is not automatic

Original Medicare pays most of a bill but not all of it. Medicare’s own Choosing a Medigap Policy booklet says the Part B share left to the patient is generally 20% of the Medicare-approved amount. Medigap policies exist to cover that share and other gaps.

Most Medicare Advantage members have no Medigap policy, because the two do not work together. Once a person goes back to Original Medicare, a supplement has to be bought fresh from a private insurer, and the same booklet warns that the company can deny a Medigap policy based on health. It adds that an insurer may also charge more for one.

The six-month window that most people have already used

The protected time for buying a supplement is the Medigap Open Enrollment Period. Medicare.gov describes it as the 6-month period that starts the first day of the month a person is 65 or older and signed up for Part B. During those six months an insurer cannot turn the applicant down or raise the price because of health problems.

The catch is timing. Someone who joined a Medicare Advantage plan at 65 and stayed for several years used up that window long ago. Their switch back in the fall of 2026 falls outside it, which is exactly where the no-guarantee rule applies.

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Who can still count on a Medigap policy after leaving

People who are leaving an Advantage plan this fall should sort themselves into one of three groups before they cancel anything. Anyone in the first group, those who joined Medicare Advantage when first eligible at 65 and are leaving within the first year, has what Medicare calls a trial right. Medicare.gov says that person has a single 12-month period, the trial right period, to get a Medigap policy back or buy one.

The second group is made up of people whose plan is the one ending. Medicare.gov lists the situations that bring a right to buy: the Advantage plan is leaving Medicare, the member is moving out of the plan’s coverage area, the plan will no longer cover where the member lives, or the plan did not follow the rules or misled the member. The third group is everyone else, and for them the insurer can say no.

The 60-day and 63-day timing

Even when a right applies, it runs on a clock. For a plan exit, Medicare.gov says the member can apply starting 60 days before the Advantage coverage ends and no more than 63 days after it ends. A person who waits past that window loses the guarantee, and the rules the insurer uses afterward are the ordinary ones.

The practical sequence matters here. A person who ends the Advantage plan before a Medigap policy is in place is left with Original Medicare alone and the 20% coinsurance. Someone who simply cancels in December and then goes shopping in January is relying on an insurer’s willingness to sell.

The question most affected readers are asking is whether they can still get a Medigap policy after leaving Medicare Advantage, and the answer depends on three facts: the date they first joined an Advantage plan, whether the plan itself is ending or leaving their county, and how many days remain in any window. Anyone who cannot place themselves in a protected group should treat the Medigap application as a medical underwriting decision, not a formality. The free guaranteed-issue rights page on Medicare.gov lays out each situation, and the state health insurance counseling program, called SHIP, can walk through them by phone at no charge.

What changes if the answer is no

An insurer that declines a Medigap application leaves the person on Original Medicare with no supplement, and with the 20% Part B coinsurance that comes with it. For someone with frequent specialist visits or an outpatient procedure on the calendar, that is the cost that decides whether leaving makes sense.

That is why the order of the decision matters more than the date. Applying to a Medigap insurer first, getting a yes in writing, and only then ending the Advantage plan keeps the person from ending up with neither coverage. Anyone who is inside a trial right or a plan-exit window has the strongest position, and a call to the insurer should say so at the start.

Open enrollment closes December 7, 2026, and changes made by then take effect January 1. Medicare.gov’s pages on when to buy remain the reference for which right applies, and they do not promise a policy to anyone outside those groups.

Leaving Medicare Advantage before December 7: will a Medigap insurer say yes?

The risk in this switch is leaving an Advantage plan on the assumption that a supplement will be sold, then learning in January that the insurer can refuse on health grounds. With the 20% Part B coinsurance left to the patient, that mistake can run for years.

The 2027 Medicare Open Enrollment Decision Kit includes Medigap guaranteed-issue rights when a Medicare Advantage plan leaves or you return to Original Medicare, with a call script, and its Medigap and IRMAA checkpoints sit beside a cost calculator spreadsheet that compares plans on cost, drugs and doctors.

Get the Medigap guaranteed-issue rights guide and call script →

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This article was produced with AI assistance and edited for accuracy against the sources linked above.