When Is Open Enrollment For Medigap? 
Open Enrollment under Federal law when you first enroll in Medicare Part B at age 65 or older , you have a guaranteed right to buy a Medicare Supplement policy for six months . Your acceptance is guaranteed and pre-existing health conditions are covered immediately . After your Open Enrollment period is over you can apply for a Medicare Supplement later at any time , but you may be charged a higher rate or be denied coverage if you have serious pre-existing health conditions . This may be your only chance to get a Medicare Supplement without having to go through medical underwriting . 