The Medicare Initial Enrollment Period (IEP) is a seven-month window that begins three months before you turn 65, includes your birthday month, and extends three months after. During this period, you can enroll in Medicare Part A and Part B. If you’re already receiving Social Security or Railroad Retirement Board benefits, you’ll be automatically enrolled in Part A and Part B three months before turning 65. Otherwise, you must enroll yourself.

The IEP also applies to Medicare Advantage plans. However, Medicare Supplement coverage has different timing. The Medicare Supplement Open Enrollment Period is a six-month window that begins the first day of the month when you are both 65 or older and enrolled in Medicare Part B. This is crucial because if you delay Part B enrollment past age 65, your Supplement Open Enrollment Period is also delayed until you actually enroll in Part B.

It’s essential to enroll during your IEP unless you have qualifying coverage elsewhere, such as through an employer. Missing your enrollment window can result in coverage gaps and late enrollment penalties of 10% for each full 12-month period you delayed signing up for Part B.