Enrollment periods and procedures differ depending on the type of Medicare plan. Enrolling in Medicare occurs over a period of seven months: during the three months before the month of your 65th birthday, the month of your birthday and the three months after your birthday month. If you're born in June, for example, your Initial Enrollment Period (IEP) is March through September.
Anyone already receiving Social Security retirement benefits qualifies for Medicare Part A and Part B and is automatically enrolled at age 65.
Individuals who are 65 and still working and who receive group health coverage through an employer, union, or spouse may delay enrolling in Part B during the IEP without incurring penalties. They may enroll at any time while still covered by a group health plan or during the eight months after that group coverage ends.
Oct. 15 through Dec. 7 is Medicare's open enrollment period, during which beneficiaries may switch plans, or join or drop Medicare Part D. Coverage begins on Jan. 1, and the Medicare Advantage disenrollment period runs from Jan. 1 through Feb. 14. During this period, enrollees may leave Medicare Advantage and enroll in Original Medicare coverage. They can also enroll in a Medicare Prescription Drug plan (Part D) [source: Medicare.gov].
Anyone who is 65 and isn't receiving Social Security retirement benefits may apply for Medicare. You can enroll online, in person at a local Social Security office or by telephone at 1-800-MEDICARE (1-800-633-4227). Open enrollment happens on an annual basis, allowing new enrollees to sign up and current beneficiaries to change coverage as needed.