Medicare Enrollment Enrolling in Medicare can be complicated, with substantial penalties for missing certain deadlines. It is important to become familiar with the enrollment process and rules, not only as you approach age 65 but also if you already have coverage. Initial Enrollment Period To avoid penalties, you should enroll during the initial enrollment period, which starts three months before the month you turn 65 and ends three months after the month you turn 65. Depending on when you enroll, coverage will start on the first day of the month indicated here. If you enroll during the... Coverage starts the... Three months before the month you turn 65 Month you turn 65 Month you turn 65 First month after enrollment First month after you turn 65 First month after enrollment Second or third month after you turn 65 First month after enrollment If you are receiving Social Security, you will be enrolled automatically in Medicare Parts A and B when you turn 65. If you are not receiving Social Security, you must apply for Medicare coverage. If you are still working and have employer-provided health coverage, it makes sense to apply for Medicare Part A when you turn 65, but you don’t have to enroll in Parts B or D, and there is no penalty. The deadline for signing up for Part B (and avoiding higher premiums) is exactly eight months after your final day of employment, regardless of when health benefits end.