If you are age 65 or older, you can purchase a Medigap Plan any time you are enrolled in Medicare Part A and Medicare Part B. If you are under age 65 there may be some additional conditions.
If you are age 65+ and enroll in a Medigap Plan within 6 months of getting Medicare Part B, your coverage is guaranteed.
If you are age 65+ and enroll in a Medigap Plan within 6 months of getting Medicare Part B, your coverage is guaranteed.