When and how to sign up for Medicare Part A and Part B
You sign up for Medicare Part A and Part B during your Initial Enrollment Period, which runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you miss this window, you can still sign up later, but you may pay a penalty for each year you delayed. The Social Security Administration handles Part A enrollment automatically if you are already receiving Social Security benefits at 65. For Part B, you must take action — it does not happen on its own.
You have three main ways to sign up: online through Medicare.gov, by phone with Social Security or Medicare, or in person at a Social Security office. Online is usually fastest. By phone, Social Security handles Part A questions at 1-800-772-1213, and Medicare handles Part B at 1-800-MEDICARE (1-800-633-4227). In person, visit your local Social Security office — no appointment needed, though wait times vary.
Key Takeaways
- Your Initial Enrollment Period is seven months long: three months before you turn 65, the month you turn 65, and three months after.
- Part A enrollment happens automatically if you receive Social Security at 65; Part B requires you to sign up separately or it will not start.
- You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
- If you miss your Initial Enrollment Period, you can still sign up later, but Part B premiums increase by 10 percent for each year you delayed.
- Your coverage start date depends on when you sign up: sign up in the month you turn 65 and coverage starts that same month.
Part A enrollment: automatic or manual, depending on your situation
If you are already getting Social Security retirement or disability benefits when you turn 65, Medicare Part A starts automatically on the first day of the month you turn 65. You do not need to do anything. Social Security sends you a Medicare card in the mail about two weeks before your coverage begins. Check it for errors — your name, date of birth, and Social Security number must be correct.
If you are not yet receiving Social Security at 65, you must sign up for Part A yourself. You can do this online at Medicare.gov, by calling Social Security at 1-800-772-1213, or at your local Social Security office. Have your Social Security number and birth certificate or passport ready. Part A has no monthly premium for most people, so the main reason to sign up is to have hospital coverage in place.
Part B enrollment: you must take action
Part B does not start automatically, even if Part A does. You must sign up during your Initial Enrollment Period or face a permanent penalty. To sign up, go to Medicare.gov, call 1-800-MEDICARE, or visit your local Social Security office. You will need your Social Security number and information about any current health coverage you have.
Part B has a monthly premium, which changes each year. In 2024, the standard premium is $164.90 per month, but yours may be higher if your income is above a certain threshold. You pay the premium through automatic deduction from your Social Security check, a bank account, or a bill sent to your home — you choose the method when you sign up.
Your Part B coverage starts on the first day of the month after you sign up, unless you sign up during the month you turn 65. If you sign up in the month you turn 65, coverage can start that same month. This timing matters: if you turn 65 in March and sign up in March, Part B starts April 1. If you sign up in April, Part B starts May 1.
What happens if you miss your Initial Enrollment Period
If you do not sign up for Part B during your seven-month Initial Enrollment Period, you can still sign up later during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage would then start July 1. However, your monthly premium increases by 10 percent for each full year you delayed. This penalty is permanent — it stays with you for life, even if you switch plans later.
There are exceptions to this penalty. If you had creditable coverage (health insurance through an employer or union) when you turned 65, you may not owe a penalty. You have eight months after that coverage ends to sign up for Part B without penalty. You will need to show proof of that coverage, so keep your insurance cards and documents.
Documents and information you will need
Gather these items before you sign up, whether online, by phone, or in person:
- Your Social Security number
- Your birth certificate, passport, or other government-issued ID
- Information about any current health insurance (employer coverage, COBRA, Medicaid, or private insurance)
- Your bank account number and routing number if you want to pay your Part B premium by automatic bank withdrawal
If you are signing up in person or by phone, the representative will ask whether you have other coverage. Be honest about this — it affects whether you owe a late penalty and whether you should sign up for Part B right away or wait.
Timeline: when coverage starts after you sign up
The start date of your coverage depends on when you sign up during your Initial Enrollment Period:
| When you sign up | When Part A starts | When Part B starts |
|---|---|---|
| Three months before you turn 65 | Month you turn 65 | Month you turn 65 |
| Month you turn 65 | Month you turn 65 | Month you turn 65 |
| One month after you turn 65 | Month you turn 65 | Following month |
| Two months after you turn 65 | Month you turn 65 | Two months later |
| Three months after you turn 65 | Month you turn 65 | Three months later |
If you sign up during the General Enrollment Period (January through March), coverage starts July 1 of that year, regardless of when in those three months you sign up.
What to do after you sign up
After you sign up, watch for your Medicare card in the mail. It usually arrives within two weeks. Check it carefully: your name, date of birth, and Social Security number must match your records exactly. If something is wrong, call Medicare at 1-800-MEDICARE to correct it before your coverage starts.
If you signed up for Part B, your first premium bill will arrive before your coverage starts. You can pay online, by phone, by mail, or through automatic withdrawal. Set up automatic payment if possible — it is the easiest way to make sure you never miss a payment.
Review your coverage options. Part A and Part B are Original Medicare. You can also choose Medicare Advantage (Part C) or add prescription drug coverage (Part D) during your Initial Enrollment Period. These decisions can wait until after you sign up for Part A and B, but the sooner you understand your options, the better.
Questions to ask your doctor or Medicare representative
Before or after you sign up, ask your doctor or a Medicare representative these questions:
- Does my current doctor accept Medicare Part B?
- Will my prescriptions be covered under Original Medicare, or do I need Part D?
- Should I sign up for Part B right away, or can I wait without a penalty?
- What is the difference between Original Medicare and Medicare Advantage for my situation?
Frequently Asked Questions
What if I am still working at 65 and have employer health insurance?
You may not need to sign up for Part B right away. If your employer has 20 or more employees, your group health plan is primary and Medicare is secondary. You can delay Part B without penalty as long as you are covered by that employer plan. When you leave your job or lose that coverage, you have eight months to sign up for Part B without penalty. Keep your insurance documents to prove you had creditable coverage.
Can I sign up for Part A without Part B?
Yes. Part A covers hospital stays, and Part B covers doctor visits and outpatient care. You can have Part A alone, though most people sign up for both. If you have other coverage for doctor visits, you might delay Part B, but understand the penalty rules first.
What if I turn 65 outside the United States?
You can still sign up for Medicare. You have the same seven-month Initial Enrollment Period. Sign up online at Medicare.gov or call Social Security at 1-800-772-1213. Your coverage works in the United States and some U.S. territories, but not in other countries, so review your travel plans before you sign up.
Do I have to sign up for Part B if I do not want it?
You do not have to sign up for Part B, but if you delay and later change your mind, you will owe a permanent 10 percent premium increase for each year you waited — unless you had creditable coverage. Think carefully before declining Part B, because that penalty is permanent.
How do I know if my sign-up was successful?
You will receive a Medicare card in the mail within two weeks of signing up. If you do not receive it by the time your coverage should start, call Medicare at 1-800-MEDICARE. They can confirm your enrollment and send a replacement card if needed.