Annual Enrollment Period (October 15 – December 7) The Annual Election Period (AEP) begins on October 15 and ends on December 7 each year. During AEP, you can enroll, disenroll or change your Medicare Advantage (MA) plan, prescription drug plan (PDP) or Medicare Supplement plan. You can also return to Original Medicare. Elections made during AEP are effective on January 1 of the following year.