A federal rule most Medicare Advantage enrollees never have reason to think about becomes relevant the moment an insurer drops their plan: for a limited stretch afterward, they get a guaranteed right to buy a Medigap policy, regardless of their health history. With more than a million Medicare Advantage members losing coverage for 2027, that guaranteed-issue right is about to matter to far more households than usual, and the people who let the window close face medical underwriting that can price a policy out of reach entirely.
The Federal Rule Behind the One-Time Medigap Window
Under Medicare’s rules, someone who loses a Medicare Advantage plan because the insurer stopped offering it, left their service area, or ended its contract with the Centers for Medicare and Medicaid Services becomes eligible for a guaranteed-issue right to a Medigap policy, according to Medicare’s own guidance. During that window, an insurer selling Medigap must sell the enrollee an eligible policy without reviewing their medical history and without charging a higher premium because of a health condition. Outside that window, most states allow Medigap carriers to underwrite applicants, which can mean denial or a steep surcharge for someone with a chronic diagnosis.
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The 63-Day Clock and What Voids It
The guaranteed-issue right generally runs for 63 calendar days after the old Medicare Advantage coverage ends, according to the Center for Medicare Advocacy, a nonprofit legal-policy organization that tracks the rule. Miss that window and the guarantee is gone; a carrier can then ask about cancer, heart disease, diabetes or other conditions and price the policy accordingly, or decline to sell it at all in states that allow underwriting. The clock starts on the coverage end date printed in the non-renewal notice, not on the date the letter arrives, which is why insurers are required to send that notice well before the plan year closes.
The termination letter itself is the document that unlocks the window, and it is easy to set aside as routine mail, according to reporting on the notice requirement. Federal rules require the letter to state plainly that the enrollee has a right to buy a Medigap policy without medical underwriting, along with the deadline for doing so, but the guarantee only helps someone who reads that section and acts before it lapses. Beneficiaries who are unsure whether their notice qualifies can call their State Health Insurance Assistance Program, a federally funded counseling service available in every state at no cost, to confirm their guaranteed-issue status before applying.
Choosing Between a New Medicare Advantage Plan and Original Medicare Plus Medigap
The right does not force anyone to buy a Medigap policy; it simply removes the medical-underwriting barrier for those who want to move to Original Medicare with supplemental coverage instead of enrolling in another Medicare Advantage plan. That decision usually comes down to cost versus flexibility: a Medigap policy typically carries a higher monthly premium than a Medicare Advantage plan but allows visits to any provider who accepts Medicare, without the referrals or prior authorizations common in Advantage networks. Someone weighing the choice during this fall’s enrollment period has both paths open at once, but only for as long as the guaranteed-issue window and the annual enrollment period overlap.
For anyone who became Medicare-eligible after Jan. 1, 2020, the strongest standardized Medigap policy available is Plan G, since the older, more comprehensive Plans C and F are closed to that group by federal law. Enrollees using their one-time guaranteed-issue right can apply for Plan G, or for a more limited plan, from any insurer licensed to sell Medigap in their state, and the insurer cannot reject the application or charge a health-based surcharge as long as the application is filed inside the guaranteed window. That protection exists precisely because the loss of a plan was not the enrollee’s choice, and it is designed to keep an involuntary plan termination from turning into a permanent coverage penalty.
Reading a Notice Before the Guaranteed-Issue Clock Starts
The guaranteed-issue right above only helps someone who acts inside a fixed number of days, and a termination letter rarely spells out what a comparable Medigap policy would actually cost, or whether a different Medicare Advantage plan might cover the same doctors without any underwriting question at all.
The 2027 Medicare Open Enrollment Decision Kit is a 42-page decision kit that pairs a cost calculator spreadsheet comparing plans on cost, drugs and doctors with a provider call script for confirming coverage before a window closes.
Read the provider call script in The 2027 Medicare Open Enrollment Decision Kit.
This article was researched and drafted with the assistance of AI tools and reviewed by The Financial Wire editorial team.
David M. Keller is a finance writer based in Columbus, Ohio, covering personal finance and consumer-focused economic topics. He earned his degree in journalism from Ohio University and began his career reporting on local business and economic trends for a regional media outlet. Since then, he has contributed to a variety of online publications, focusing on clear, practical coverage of topics such as cost of living, debt, and everyday financial decision-making.
