Did You Know: Trial right guaranteed issue right or SEP-65
You joined a Medicare Advantage Plan or Program of All-inclusive Care for the Elderly (PACE) when you were first eligible for Medicare Part A at 65, and within the first year of joining, you decide you want to switch to a Medicare Supplement and Part D Prescription Drug Plan. *Tip: If you enrolled after the age of 65, this does not apply to your situation.
You dropped a Medigap policy to join a Medicare Advantage Plan (or to switch to a Medicare SELECT policy) for the first time, you’ve been in the plan less than a year, and you want to switch back. *Tip: You must switch back to your prior plan, unless it isn’t available.
In both circumstances, you have 63 calendar days after your coverage ends to make your changes.
Special Enrollment Periods: https://www.medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan/special-enrollment-periods