You can typically enroll in Medicare when you first turn 65. Generally, there are risks to signing up later, like a gap in coverage or having to pay a penalty. However, in some cases, it might make sense to sign up later.

No matter when you want to sign up, you need to signup during one of the defined enrollment periods.

You can read in depth about Enrollment Periods here.

Initial Enrollment Period

This is the 7 month window around your birth month during with you are first eligible to sign up for Medicare without a penalty. The period starts 3 months prior to your month and ends 3 months after your birth month.

Special Enrollment Period

If you miss your Initial Enrollment Period but have certain qualifying situations, like being covered by employer insurance, you may have a Special Enrollment Period.

Typical SEPs include moving, loss of other coverage, or change in family size.

General Enrollment Period

If you don’t enroll during your Initial or Special Enrollment Period, you will need to wait and enroll between January 1 and March 31 each year, but you may have to pay a late enrollment penalty. 

Automatic Enrollment

If you are already receiving Social Security benefits, or Railroad benefits, when you turn 65, you will be automatically enrolled in Medicare Part A and Part B.