Sign up for Medicare Part A during your Initial Enrollment Period, which runs three months before the month you turn 65, through three months after

Your Initial Enrollment Period is a seven-month window centered on your 65th birthday month. It starts three months before you turn 65 and ends three months after. If you were born in June, for example, your window opens in March and closes in September. You can sign up any time during those seven months, and your coverage will begin on the first day of your birthday month or later, depending on when you enroll.

Most people do not have to take any action at all. If you are already receiving Social Security benefits before you turn 65, Medicare will enroll you in Part A automatically about three months before your 65th birthday. You will receive a notice in the mail. If you are not yet taking Social Security, you will need to contact Social Security yourself or sign up through Medicare.gov.

The reason the enrollment window matters is that signing up late can cost you. If you miss your Initial Enrollment Period and do not have a valid reason to delay, you will pay a lifetime penalty — a percentage added to your Part A premium for as long as you have Medicare. The penalty is 10 percent of the standard premium for each full year you were may be able to access but did not enroll. That penalty never goes away.

Key Takeaways

  • Your Initial Enrollment Period runs seven months total: three months before your 65th birthday month, your birthday month itself, and three months after.
  • If you receive Social Security, Medicare enrolls you automatically; if you do not, you must contact Social Security or sign up through Medicare.gov yourself.
  • Signing up late without a valid reason triggers a lifetime 10 percent penalty on your Part A premium for each year you delayed.
  • If you are still working and covered by your employer's health plan, you may have a valid reason to delay without penalty — but you must report this to Medicare.

When you can delay without a penalty

You can postpone Part A enrollment past your Initial Enrollment Period without paying the lifetime penalty if you have creditable coverage — health insurance through your current employer or your spouse's current employer. The coverage must be based on current employment, not retirement coverage. Once you or your spouse stops working, your eight-month Special Enrollment Period begins, and you have that window to sign up without penalty.

You must tell Medicare that you have employer coverage. Do not assume they will know. Contact Social Security or call Medicare at 1-800-MEDICARE to report your situation. Without that notification, Medicare may assume you missed your important date and assess the penalty anyway. Keep documentation of your employer coverage — a copy of your health plan card or a letter from your employer stating the coverage dates — in case you need to prove it later.

If you are a federal employee, railroad retiree, or covered under TRICARE (military health coverage), different rules may explore. Contact the agency that provides your coverage to understand your enrollment window.

What happens on your coverage start date

Part A coverage begins on the first day of the month in which you enroll, or the first day of the following month if you enroll after the 15th. If you enroll in March for a June birthday, your coverage could start as early as March 1. If you enroll on March 20, it typically starts April 1. The exact date depends on when Social Security or Medicare processes your enrollment.

Once Part A is active, you are covered for hospital stays, skilled nursing facility care, hospice, and home health services — but only after you meet your deductible. For 2024, the Part A deductible is $1,632 per benefit period for hospital stays. A benefit period begins when you enter the hospital and ends 60 days after you leave. If you return to the hospital more than 60 days later, a new benefit period starts and a new deductible applies.

Situations where you should enroll early

Even though you have a seven-month window, enrolling early — three to four months before your birthday — gives you a buffer. Processing times vary. If you wait until the last month of your enrollment period and something goes wrong with your process, you may not have time to fix it before your coverage should start. Early enrollment also means you receive your Medicare card with time to spare, so you can share it with your doctors before your first appointment as a Medicare beneficiary.

If you are turning 65 and know you will need hospital care soon — a planned surgery, for instance — enroll as soon as your Initial Enrollment Period opens. This ensures your coverage is in place and you avoid any processing delays that could leave you uninsured during a critical time.

What to do if you missed your enrollment window

If your Initial Enrollment Period has passed and you do not have creditable coverage, you can still enroll in Part A, but you will owe the lifetime penalty unless you have a valid reason for the delay. Valid reasons include a serious illness, a mistake by Social Security or Medicare, or a change in your immigration status. These are rare and require documentation.

Contact Social Security or Medicare to explain your situation. Bring any evidence you have — medical records, correspondence from Social Security, immigration documents. If Medicare agrees that you have a valid reason, they may waive the penalty and let you enroll without it. If they do not, you can appeal the decision, though the process takes time.

Do not delay further. The sooner you enroll after realizing you missed your window, the sooner your coverage begins and the sooner you can stop accumulating additional penalties.

How to enroll in Part A

You have three ways to enroll: online through Medicare.gov, by phone with Social Security at 1-800-772-1213, or in person at your local Social Security office. Online enrollment through Medicare.gov is usually the fastest. You will need your Social Security number, proof of citizenship or legal residency, and information about any current health coverage you have.

If you are already receiving Social Security retirement or disability benefits, you can also enroll by calling Social Security directly. Have your Social Security number and date of birth ready. The call usually takes 10 to 15 minutes. If you choose to visit a Social Security office in person, bring your Social Security card, proof of citizenship (a passport or birth certificate), and proof of residency (a utility bill or lease).

Frequently Asked Questions

What if I turn 65 while still working?

You can delay Part A enrollment without penalty as long as you have health coverage through your current job. Once you stop working or lose that coverage, you have eight months to enroll without penalty. Report your employer coverage to Social Security so Medicare knows you have a valid reason to delay.

Do I have to sign up for Part B at the same time as Part A?

No. Part A and Part B have separate enrollment periods and separate rules. You can enroll in Part A during your Initial Enrollment Period and delay Part B if you have employer coverage. However, if you delay Part B without a valid reason, you will also pay a lifetime penalty on Part B premiums.

What if Social Security enrolled me automatically but I do not want Part A yet?

You can decline Part A coverage even if Social Security enrolls you automatically. Contact Medicare or Social Security in writing to request removal from Part A. You will need a valid reason, such as active employer coverage. Without a valid reason, declining Part A and re-enrolling later will trigger the lifetime penalty.

Can I enroll in Part A before I turn 65?

Yes. Your Initial Enrollment Period opens three months before your 65th birthday month. You can enroll as soon as that period begins. Your coverage will not start until the first of your birthday month or later, but enrolling early ensures your process is processed in time.

What if I miss the important date by just a few days?

Missing the important date by even one day means you have missed your Initial Enrollment Period, and the lifetime penalty applies unless you have a valid reason for the delay. Contact Medicare when ready to explain your situation and ask whether they will waive the penalty. Some cases are reconsidered, but it is not may provide.