There are specific times in which you can enroll in a Part C plan:

Initial coverage election period: Your initial coverage election period is a seven-month period that starts three months before the month you turn 65 and ends three months after the month you turn 65. If you are under 65 and receive Social Security disability, you qualify for Medicare in the 25th month after you begin receiving your Social Security benefits. If that is how you are becoming eligible for Medicare, you can enroll into an Advantage plan three months before your month of eligibility until three months after you became eligible. 

Annual election period: Also known as open enrollment or AEP, the annual election period for Medicare Advantage is October 15 through December 7 every year. Coverage for the Part C plan you choose during this time will begin January 1 the next year. During this time, you can also add, change, or drop current coverage.

Medicare Advantage Open Enrollment Period: During this open enrollment period, you are able to change from one Advantage plan to another or drop it to return to Original Medicare.

Special Election Period: There are several things that can trigger a special election period and they are unique to an individual. It is best to speak to a licensed Medicare insurance agent to find out if you qualify for a special election period. However, there are a few common instances we can talk about. Such as, if you move outside your Medicare Advantage plan’s service area, qualify for extra help (such as a program that helps pay for your prescription drugs), or move into a nursing home you might qualify for a special election period. During this time you can make changes to your Advantage plan or return back to Original Medicare.