What is the Annual Election Period (AEP)?
The Annual Election Period, or AEP, for coverage effective in a calendar year begins October 15 of the previous calendar year and ends December 7 of the previous year. During this period, anyone who is enrolled in Medicare may enroll for the first time in a Medicare Advantage Plan; or change from one Medicare Advantage Plan to another; or return to Original Medicare from a Medicare Advantage Plan. If during this period you enroll in a Medicare Advantage Plan that includes Medicare Part D prescription drug coverage then any prior Medicare Part D Plan coverage is automatically cancelled and replaced by the new Medicare Advantage Plan with prescription drug coverage — these plans are known as MA-PD plans (Medicare Advantage-Part D plans). Enrollments during this period have an effective date of January 01. The AEP occurs October 15 through December 7 every year.
from Medicare.gov, Medicare Options Compare (2016) & Medicare.gov,Medicare Plan Choices Overview (2016)
The Annual Election Period, or AEP, for coverage effective in a calendar year begins October 15 of the previous calendar year and ends December 7 of the previous year. During this period, anyone who is enrolled in Medicare may enroll for the first time in a Medicare Advantage Plan; or change from one Medicare Advantage Plan to another; or return to Original Medicare from a Medicare Advantage Plan. If during this period you enroll in a Medicare Advantage Plan that includes Medicare Part D prescription drug coverage then any prior Medicare Part D Plan coverage is automatically cancelled and replaced by the new Medicare Advantage Plan with prescription drug coverage — these plans are known as MA-PD plans (Medicare Advantage-Part D plans). Enrollments during this period have an effective date of January 01. The AEP occurs October 15 through December 7 every year.
from Medicare.gov, Medicare Options Compare (2016) & Medicare.gov,Medicare Plan Choices Overview (2016)