You can apply for Medicare during your Initial Enrollment Period (IEP), which is a seven-month window surrounding your 65th birthday. This period starts 3 months before the month of your 65th birthday, includes the month you turn 65, and ends 3 months after that month. For example, if your birthday is in June, your enrollment period runs from March 1 through September 30. If you sign up during the three months before your birthday, coverage starts the first day of your birthday month. If you sign up during your birthday month or the three months after, coverage begins the first day of the following month. If you miss this initial enrollment period, you might qualify for a Special Enrollment Period if you have certain circumstances, like being covered by an employer’s group health plan. Otherwise, you can apply during the General Enrollment Period from January 1 to March 31 each year, but your coverage will start the month after you sign up and you may face late enrollment penalties. If you are already receiving Social Security benefits when you turn 65, you may be automatically enrolled in Medicare Part A and Part B. In summary, the most common and recommended time to apply for Medicare is starting three months before you turn 65 and extending to three months after your birthday month to avoid gaps in coverage or penalties.