You can only enroll in Part B (and/or Part A if you have to buy it) during these enrollment periods.

Initial Enrollment Period

You can first sign up for Part A and/or Part B during the 7-month period that begins 3 months before the month you turn 65, includes the month you turn 65, and ends 3 months after the month you turn 65.

If you enroll in Part A and/or Part B during the first 3 months of your Initial Enrollment Period, in most cases, your coverage begins the first day of your birthday month. However, if your birthday is on the first day of the month, your coverage will start the first day of the prior month.

If you enroll in and are paying for Part A and/or Part B the month you turn 65 or during the last 3 months of your Initial Enrollment Period, the start date for your Part B coverage will be delayed.

Special Enrollment Period (SEP)

After your Initial Enrollment Period is over, you may have a chance to enroll in Medicare during a Special Enrollment Period. If you didn’t sign up for Part B (or Part A if you have to buy it) when you were first eligible because you have group health plan coverage based on current employment (your own, a spouse’s, or a family member’s—if you have a disability), you can enroll in Part A and/or Part B:

Anytime you’re still covered by the group health plan During the 8-month period that begins the month after the employment ends or the coverage ends, whichever happens first

Usually, you don’t pay a late enrollment penalty if you sign up during a Special Enrollment Period. This period doesn’t apply if you’re eligible for Medicare based on End-Stage Renal Disease (ESRD), or you’re still in your Initial Enrollment Period.

Note: If you have a disability, and the group health plan coverage is based on a family member’s current employment (other than a spouse), the employer offering the group health plan must have 100 or more employees for you to get a Special Enrollment Period.

General Enrollment Period

If you have to pay for Part A but don’t sign up for it and/or don’t sign up for Part B (for which you must pay premiums) during your Initial Enrollment Period, and you don’t qualify for a Special Enrollment Period, you can sign up during the General Enrollment Period between January 1–March 31 each year. Your coverage won’t start until July 1 of that year, and you may have to pay a higher Part A and/or Part B premium for late enrollment.

Are you eligible for Medicare Enrollment?