During select times of the year, you may join, drop, or change from one Part C plan to another. When you first qualify for Medicare, you can join an Advantage plan with OR without prescription drug coverage. This is called your Initial Enrollment Period (IEP), and it begins the three months before the month you turn 65 and ends the three months after.
The Annual Enrollment Period (AEP), is October 15 to December 7. During this time, you can join, change, or drop a Medicare Part C plan. Your coverage will kick in on January 1.
Next, the Medicare Advantage Open Enrollment (MAOEP) is from January 1 to March 31. You can switch to a different Part C plan or return to Original Medicare and enroll in a stand alone prescription drug plan, once, during this window.
Also, certain events may cause a Special Enrollment Period (SEP) where you have two months to join a Part C plan. SEPs are unique to the individual, so you should contact your Medicare insurance agent to see if you qualify.