Unlike Medicare Advantage plans, Medigap plans do not have specific enrollment periods. Participants can enroll in a Medigap plan at any time. However, without guaranteed issue, applicants have to go through medical underwriting. The carrier can adjust the premium based on health conditions or simply deny coverage.
On the other hand, without an eligible disenrollment period, participants cannot switch from a Medicare Advantage (MA) plan to a Medigap plan, because it is illegal for an agent to sell a Medigap plan to an MA participant. Therefore, to enroll in a Medigap plan, in most cases, participants have to wait until the Annual Enrollment Period (AEP). Even if a participant switches from MA to Medigap during an AEP, he/she will still be subject to medical underwriting. There are however periods of times when Medicare beneficiaries have guaranteed issue (GI) rights. The situations are summarized below.
Age In/Open Enrollment
When an individual turns 65 and becomes eligible for Medicare, there is the so-called Medigap Open Enrollment Period during which you have your first GI opportunity to enroll in a Medigap plan. More precisely, the period starts the first month you are entitled to both Medicare parts A & B, and lasts for 6 months. The open enrollment period is valid only if you are 65 or older. (In other words, this is not for people who become eligible for Medicare by aging in.)
You are during your first 12 month in an MA plan, and you would like to switch (back) to Medigap. You can apply for a Medigap plan 60 days before your MA coverage ends, and no later than 63 calendar days after the MA coverage ends.
Generally speaking, if you lose your MA/Medigap coverage due to no fault of yours (e.g., the plan ends contract with Medicare, the insurance carrier goes bankrupt, etc.), you get a GI opportunity to enroll in Medigap. Moving out of MA plan’s service area is also considered involuntary disenrollment. In that case, if you switch back to the original Medicare instead of getting another MA, you get a Medigap GI. You must apply for a Medigap within 63 days after your coverage ends in order to get a GI.
Losing a Group Coverage
Medicare beneficiary is losing a group/union/COBRA plan coverage that is a secondary payer after Medicare (in other words, the beneficiary is entitled to both parts A & B), the beneficiary has 63 days after the coverage ends. If the individual is losing a group coverage that is the primary payer (before Medicare pays), the individual does not need to have part B before the coverage ends. He/she can then enroll in part B and have the 6-month open enrollment period.