The Situation This Covers
Medicare calls this a guaranteed-issue right. An insurance company must sell you a Medigap policy, must cover your pre-existing conditions, and cannot charge you more because of your health. For people 65 or older, this particular right applies when any of these happens:
- Your Medicare Advantage plan is leaving Medicare
- Your plan stops providing care in your area
- You move out of the plan's service area
The letter from the plan is what proves it. Keep that notice. If a company is mapping you into a different plan instead of ending coverage, the notice says whether this right applies. People on Medicare because of a disability, under 65, should confirm the state rule before assuming the same plans are for sale.
You Have to Choose Original Medicare
The right to buy a supplement exists if you switch to Original Medicare. Joining another Medicare Advantage plan uses a different path, and Medigap will not pay alongside it.
Original Medicare plus a supplement is Part A and Part B, a Medigap policy that helps pay Medicare cost-sharing, and a separate Part D plan for prescriptions. You keep paying the Part B premium. The supplement has its own premium. Any doctor in the country who takes Medicare is available to you. The Medicare Supplement guide explains how the lettered plans differ once you are allowed to buy one.
Which Letters Are Guaranteed
In this situation, federal rules say you can buy any of these that an insurer sells in your state:
- Plan A
- Plan B
- Plan C
- Plan D
- Plan F
- Plan G
- Plan K
- Plan L
Plan G is on that list. Plan N is not. Plans C and F, which cover the Part B deductible, are not sold to anyone who became newly eligible for Medicare on or after January 1, 2020. If you were already eligible before that date, you may still be able to buy one.
The Clock
Apply as early as 60 days before the Medicare Advantage coverage ends, and no later than 63 days after it ends. The Medigap policy cannot start until the Medicare Advantage coverage ends, so ask for it to begin the day that coverage stops.
If a plan ends on December 31, that window runs well past December 7, when Annual Enrollment closes. The drug-plan deadline is a separate date. Leaving a gap without creditable drug coverage can create a Part D late-enrollment penalty. The Part D guide covers that penalty. Use the dates on your plan's notice for the drug plan, and do not assume they match the Medigap 63 days.
Doing Nothing Is Not a Supplement
If the plan ends and there is no replacement plan you are enrolled in, doing nothing generally puts you back on Original Medicare on January 1, without drug coverage and without a Medigap policy. The guaranteed-issue right is an application you have to submit. It is not added for you.
This Is Not the Oregon or Washington Switching Rule
Oregon's birthday rule and Washington's year-round right to switch Medigap letters apply when you already have a Medigap policy. Coming from Medicare Advantage, the right that gets you in the door is this federal window. After you have a policy, those state rules can matter the next time you want to change letters. The details are in the Oregon & Washington rules guide.
There is a separate trial right, too. If you joined a Medicare Advantage plan when you first became eligible for Medicare at 65, and you leave it within the first 12 months, you can buy any Medigap policy sold in your state. If you dropped a Medigap policy to try Medicare Advantage for the first time and you leave within 12 months, you can return to the policy you had, or to plans A, B, C, D, F, G, K, or L if that old policy is no longer sold. That trial is a different fact pattern from a plan shutting down.
What This Means in Oregon and Washington for 2027
Several Medicare Advantage plans are leaving counties in Oregon and Washington at the end of 2026. Which companies, and which counties, are on the 2027 Medicare changes page. If your notice says the plan is ending or leaving your county, this guaranteed-issue window is the reason Original Medicare plus a supplement is on the table even when you are well past your original Medigap Open Enrollment.