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Understanding Medicare

Enrolling in Medicare: The Deadlines

Pay attention to these windows of opportunity,
or pay a price

It’s best to enroll in Medicare during the following seven-month window. This is called your Initial Enrollment Period (IEP):

• Three months before your 65th birthday
• The month of your 65th birthday
• Three months after your 65th birthday

An exception: If you are already receiving Social Security or Railroad Retirement Board benefits, you are automatically enrolled in Original Medicare — Parts A and B. If you want to consider a Medicare Advantage (Part C) plan, check with Medicare about these enrollment opportunities.

You can enroll later if you miss your initial enrollment window, but you may face penalties. The best time to sign up for Medicare is during the three months before your 65th birthday, so everything will be in place and you can begin receiving benefits.

You can sign up for Medicare at your local Social Security office or by applying online at

It’s advisable to enroll in the Medicare program during your Initial Enrollment Period, even if you won't be using all, or any, of the program's benefits to begin with. Why?

If when you are first eligible you don’t enroll in Part B or Part D (which are optional and, unlike Part A, involve monthly premiums), and you don’t qualify for an exemption or special enrollment period, you could be charged higher premiums and a late enrollment penalty. Not only that, you might be limited by the times of year in which you can enroll.

For examples of situations in which higher costs were applied, see the AARP Ms. Medicare column about Medicare penalties and the AARP Bulletin article "COBRA Bites Back."

Medigap is an optional, supplemental insurance you can purchase to help pay for some of the health costs Medicare doesn’t cover. The best time to buy a Medigap policy is during your Medigap open enrollment period, which lasts for six months and begins on the first day of the month in which you are both 65 or older and enrolled in Medicare Part B.

During this period, you can buy a Medigap policy without fear of being turned down or charged more because of a past or present health problem. After this six-month period, you may be denied coverage or charged more due to a pre-existing condition. If you join a Medicare Advantage plan, also called Part C, you don’t need and can’t be sold a Medigap policy.

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Download a PDF of AARP's "Understanding Medicare" guide or request a copy by mail.

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