A federal guaranteed-issue right lets a Medicare Advantage enrollee whose plan is leaving Medicare, exiting the enrollee’s county, or misrepresenting its coverage buy any Medigap policy sold in the state without answering a single medical question. Medicare’s own guidance places the window at 60 days before the Medicare Advantage coverage actually ends through 63 days after it ends, a 123-day span split unevenly around the termination date. Beneficiaries who wait until their Advantage coverage has already lapsed before applying have, by definition, spent the front half of that window doing nothing. The distinction determines whether an insurer must sell a Medigap policy at any price or can turn an applicant away entirely.
The 123-Day Window Read Backward
Most consumer explanations of Medicare guaranteed-issue rights describe the protection as something that activates once a plan’s coverage has ended, treating 63 days as the operative number. That framing captures only the back half of the actual rule. Medicare’s guidance is explicit that the application period begins 60 calendar days before the termination date, meaning the right to buy exists while the Medicare Advantage plan is still technically providing coverage. An enrollee who receives notice that a plan is leaving Medicare or exiting a service area does not have to wait for a lapse in coverage to start shopping for a Medigap policy; waiting is itself what erodes the protection.
The right applies only if the enrollee switches to Original Medicare rather than joining a different Medicare Advantage plan, and Medigap coverage cannot begin until the old coverage actually terminates. If the enrollee never held a Medigap policy before joining Medicare Advantage, the choice of Medigap plans is limited to Plans A, B, C, D, F, G, K or L sold by an insurer in that state, and the insurer cannot use medical underwriting to deny the application or raise the price based on a pre-existing condition.
That eight-plan list is narrower than the roster generally available during a person’s initial Medigap Open Enrollment Period, and it excludes Plan N, which several insurers otherwise sell. An enrollee who did carry a Medigap policy before ever joining Medicare Advantage keeps a separate, related right: buying back that exact former policy from the same insurer, if the company still sells it, rather than choosing fresh among the eight standardized plans.
Free plan-change checklist: A Medicare plan can change its costs, drugs and doctors for next year even when its name stays the same. Check the changes with the free 2027 review sheet.
What the Guaranteed-Issue Right Is Not
Guaranteed issue is the exception, not the default path into a Medigap policy. Federal law otherwise gives beneficiaries a one-time, six-month Medigap Open Enrollment Period that starts the first month someone is 65 or older and enrolled in Medicare Part B; outside that window, an insurer can generally deny an application or charge more based on health history. Guaranteed-issue rights exist specifically to cover situations, like an involuntary Medicare Advantage termination, where a beneficiary loses coverage through no choice of their own and would otherwise face medical underwriting a second time.
That structure means the right does not apply to someone who simply decides they no longer like their Medicare Advantage plan and wants to leave voluntarily. It is reserved for terminations initiated by the plan itself: exiting Medicare altogether, dropping a service area, or, separately, a documented case of the plan misleading the enrollee or violating marketing rules. A beneficiary who voluntarily switches to Original Medicare during the annual Open Enrollment Period without one of those triggers has no federal guarantee that any insurer will sell a Medigap policy at all.
Why the Front End Gets Missed
The timing collision that erases the front half of the window is structural. Medicare Advantage plan years run on a calendar-year cycle, and insurers that intend to leave a county or exit Medicare notify CMS and enrollees during the same fall stretch that overlaps the annual Medicare Open Enrollment Period, which runs October 15 through December 7. A plan ending on December 31 puts the guaranteed-issue window’s opening date around November 1 — while the enrollee’s attention, and most of the surrounding news coverage, is focused on the plan-comparison deadline in early December, not on a Medigap application clock that has already started.
An enrollee who treats January 1, the date new coverage typically begins, as the moment to start thinking about Medigap has not lost the entire window, but has already lost the 60-day portion that carried no urgency, no lapse in coverage and no need to prove anything after the fact. The remaining 63 days after termination still work, but they compress a decision that could have started two months earlier into a matter of weeks.
That compressed timeline carries a coverage-gap risk as well as a paperwork risk. Original Medicare continues paying its share of claims throughout the transition, but without a Medigap policy in force, the enrollee absorbs the coinsurance and deductibles Medigap exists to cover until a new policy actually takes effect — exposure that lasts exactly as long as the enrollee delayed applying.
The Proof That Makes the Right Enforceable
Because the guaranteed-issue right is an exception to ordinary underwriting, insurers can require documentation before honoring it. Medicare’s guidance instructs beneficiaries to keep letters, notices, emails or claim denials connected to the Medicare Advantage termination, since a new Medigap application may need those documents attached as proof the applicant qualifies. An application submitted without that paper trail risks being treated as an ordinary application subject to medical underwriting, which defeats the purpose of applying inside the guaranteed-issue window in the first place.
Medicare’s guidance also notes that some beneficiaries’ rights can extend an additional 12 months under specific circumstances, and that state insurance regulators can grant broader protections than the federal minimum. Neither exception changes the federal baseline: the clock starts 60 days before a Medicare Advantage termination takes effect, not after, and the beneficiaries most likely to lose that half of the window are the ones who treat the termination date, rather than the notice that preceded it, as the moment guaranteed issue begins.
Mapping the Switch Windows a Dropped Plan Opens
The same fall stretch that starts a guaranteed-issue Medigap clock also runs the annual Medicare Open Enrollment Period, when every Medicare Advantage and Original Medicare enrollee can compare costs, drug coverage and provider networks for the year ahead. Lining up a plan’s termination date, an Annual Notice of Change, and a Medigap application deadline means tracking several dates that live in different notices and rarely appear side by side. Comparing what a replacement Medicare Advantage plan actually covers against what Original Medicare plus a Medigap policy would cost typically means working through a plan’s drug list and provider network by hand.
The 2027 Medicare Open Enrollment Decision Kit is a 42-page decision kit built around a cost calculator spreadsheet that compares plans on cost, drugs and doctors, a prescription-by-plan comparison, and the Open Enrollment calendar that lines up the relevant deadlines.
Compare the cost calculator and the Open Enrollment calendar in The 2027 Medicare Open Enrollment Decision Kit.
This article was researched and drafted with the assistance of AI and reviewed by The Money Overview editorial team.
