There are four periods during which you can enroll in premium Part A: Initial Enrollment Period (IEP), General Enrollment Period (GEP), Special Enrollment Period (SEP), and Transfer Enrollment Period (TEP).

• Initial Enrollment Period: The IEP is the first chance you have to enroll in premium Part A. Your IEP starts 3 months before you first meet all the eligibility requirements for Medicare and continues for 7 months.
• General Enrollment Period: January 1 through March 31 of each year. Your premium Part A coverage is effective July 1 after the GEP in which you enroll.
• Special Enrollment Period: The SEP is for people who did not take premium Part A during their IEP because you or your spouse currently work and have group health plan coverage through your current employer or union. You can sign up for premium Part A at any time you are covered under the Group Health Plan based on current employment. If the employment or group health coverage ends, you have 8 months to sign up. The 8 months start the month after the employment ends or the group health coverage ends, whichever comes first.
• Transfer Enrollment Period: The TEP is for people age 65 or older who have Part B only and are enrolled in a Medicare managed care plan. You can sign up for premium Part A during any month in which you are enrolled in a Medicare managed care plan. If you leave the plan or if the plan coverage ends, you have 8 months to sign up. The 8 months start the month after the month you leave the plan or the plan coverage ends. If you enroll in Part B or Part A (if you don't get it automatically without paying a premium) during the GEP, your coverage starts on July 1. (See Enrollment.)