Most people get Medicare Part A automatically, but you must act during your enrollment window or face penalties

If you are receiving Social Security benefits before age 65, Medicare Part A (hospital insurance) starts automatically the month you turn 65. You do nothing. But if you are still working and have not claimed Social Security, you must enroll during your Initial Enrollment Period — a seven-month window that starts three months before the month you turn 65 and ends three months after. Missing this window costs you permanently: you pay a 10 percent penalty on your Part A premium for each year you could have had it but did not.

The three ways to enroll are online through Medicare.gov, by phone with Social Security, or in person at a Social Security office. Online is fastest — you can complete it in 10 minutes if your information is current in the Social Security system. The phone line has longer wait times but a real person can answer questions about your specific situation. In-person enrollment at a Social Security office takes longer but guarantees a receipt.

Key Takeaways

  • If you receive Social Security before 65, Part A starts automatically; if you do not, you must enroll during your seven-month Initial Enrollment Period or pay a permanent 10 percent penalty.
  • Your Initial Enrollment Period runs from three months before you turn 65 through three months after, and the Social Security Administration counts the month you turn 65 as month one.
  • You can enroll online at Medicare.gov, by phone at 1-800-772-1213 (Social Security), or at your local Social Security office with only your Social Security number and proof of citizenship.
  • Part A has no monthly premium for most people, but you must also enroll in Part B during the same window or face a separate 10 percent penalty on Part B premiums.
  • If you miss your Initial Enrollment Period, you can enroll during the General Enrollment Period (January 1 to March 31 each year), but the penalty applies retroactively to when you should have enrolled.

When your seven-month enrollment window opens and closes

Your Initial Enrollment Period is centered on the month you turn 65. It begins three calendar months before that month and ends three calendar months after. If you turn 65 in June, your window opens in March and closes in September. The Social Security Administration counts the month you turn 65 as the middle month, not as month one.

You should enroll as early as possible within this window — ideally in the first month it opens. If you wait until the last month and something goes wrong with your process (a missing document, an error in your records, a system delay), you have no buffer. Enrolling early also means your coverage can start on the first day of the month you turn 65, rather than later if you explore near the important date.

If you are still working and covered by your employer's health plan, you may be able to delay Part A enrollment without penalty under special rules called creditable coverage. This is rare and requires your employer plan to be as good as Medicare. Do not assume you may have access to — contact Social Security to ask before you skip enrollment.

Enrolling online through Medicare.gov

Go to Medicare.gov and click "Sign up for Medicare" in the top menu. You will be asked to create a Medicare.gov account or log in if you have one already. You will need your Social Security number, date of birth, and mailing address. The system will pull your information from Social Security records, so make sure your name, address, and citizenship status are correct there first — if they are wrong, the online process may fail or take longer to process.

The online form asks whether you want Part A, Part B, or both. You should enroll in both during your Initial Enrollment Period unless you have employer coverage that qualifies as creditable. The form takes about 10 minutes. At the end, you will see a confirmation number on screen — write it down or take a screenshot. Medicare will also email a confirmation, though it may take a few hours to arrive.

Online enrollment is fastest because it goes straight into the Medicare system. You should receive a Medicare card in the mail within two to four weeks. If you do not receive it by the time your coverage is supposed to start, call 1-800-MEDICARE to confirm your enrollment went through.

Enrolling by phone with Social Security

Call Social Security at 1-800-772-1213 (TTY 1-711). Wait times are longest on Tuesdays through Thursdays and in the morning. Have your Social Security number, date of birth, and citizenship information ready. A representative will ask whether you want Part A, Part B, or both, and will confirm your address and contact information.

The representative will give you a confirmation number at the end of the call. Ask them to repeat it and write it down. They will also tell you when to expect your Medicare card. If you do not receive it by that date, call back with your confirmation number.

Phone enrollment takes longer than online because of wait times, but it is useful if your information in the Social Security system is outdated or if you have questions about whether you may have access to for a penalty exemption. The representative can also tell you on the spot whether your employer coverage counts as creditable.

Enrolling in person at a Social Security office

Find your local Social Security office at ssa.gov/locator. You can walk in during business hours, but many offices now require an appointment. Call ahead or book online to avoid a long wait. Bring your Social Security card (or a document with your number), proof of citizenship (passport, birth certificate, or naturalization papers), and proof of your current address (utility bill, lease, or bank statement dated within the last 60 days).

The office staff will fill out your Medicare enrollment form with you and give you a receipt on the spot. This receipt is your proof of enrollment if anything goes wrong later. Keep it until your Medicare card arrives. In-person enrollment is slower than online or phone, but it is the best option if you want a physical record or if you have complex questions about your situation.

What happens after you enroll

Once you enroll, Medicare processes your process within one to two weeks. Your Part A coverage starts on the first day of the month you turn 65 (or the first day of the month after you enroll, if you enroll after you turn 65). You will receive a Medicare card in the mail showing your Medicare number, your name, and the date your coverage starts. The card is not required to use Medicare — hospitals and doctors can look you up by your Social Security number — but you should keep it in your wallet.

Part A has no monthly premium for most people because you paid into it through payroll taxes while you worked. However, Part A does have a deductible: as of 2024, you pay $1,676 for each benefit period for hospital stays. A benefit period starts 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 begins and you pay the deductible again.

If you also enrolled in Part B, your Part B premium will be deducted from your Social Security check each month starting the month your coverage begins. If you do not receive Social Security, Medicare will bill you directly.

If you miss your enrollment window

If you do not enroll during your seven-month Initial Enrollment Period, you can still enroll, but you will pay a penalty. The General Enrollment Period runs January 1 through March 31 each year. You can enroll then, and your coverage will start July 1 of that year. However, you will owe a 10 percent penalty on your Part A premium for each full year you could have had Part A but did not. If you were may be able to access to enroll five years ago and did not, you pay 50 percent extra on your Part A premium for the rest of your life.

The only way to avoid this penalty is to show that you had creditable coverage (employer or union health insurance as good as Medicare) for the entire time you were not enrolled. You must provide proof — usually a letter from your employer or former employer stating the dates you were covered and that the plan was creditable. Without this proof, the penalty applies.

If you are already past your Initial Enrollment Period and did not have creditable coverage, contact Social Security anyway. Some people may have access to for a Special Enrollment Period if they had a life event like losing employer coverage or moving to a new state. Social Security can tell you whether you may have access to.

Frequently Asked Questions

Do I have to enroll in Part B at the same time as Part A?

You do not have to, but you should during your Initial Enrollment Period. If you delay Part B enrollment, you will pay a 10 percent penalty on your Part B premium for each year you could have had it but did not. The only exception is if you are still working and covered by your employer's health plan — in that case, you can delay Part B without penalty, but you must enroll within eight months of losing that coverage.

What if my name or address is wrong in the Social Security system?

Contact Social Security before you enroll in Medicare. Call 1-800-772-1213 or visit your local office. They can correct your records, and the correction will show up in Medicare within a few days. If you enroll with wrong information, your Medicare card will have the wrong name or address, and you may have trouble using it at the hospital.

Can I enroll in Medicare before I turn 65?

No. Your Initial Enrollment Period does not open until three months before the month you turn 65. If you try to enroll earlier, the system will reject your process. You can prepare by making sure your Social Security records are correct and by gathering your documents, but you cannot submit an enrollment form until your window opens.

What if I am not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident (green card holder) who has lived in the United States for at least five years to enroll in Medicare. If you are a permanent resident, bring your green card when you enroll. If you do not meet these requirements, you do not may have access to for Medicare, and you should explore other health insurance options.

Will I owe back premiums if I enroll late?

No. You will owe the penalty (10 percent extra on your premium), but you do not owe premiums for the months before you enrolled. Your coverage and premium payments start the month your enrollment becomes effective, which is usually July 1 if you enroll during the General Enrollment Period.