When and How to Register for Part B

Medicare Part B covers doctor visits, outpatient care, and medical equipment. You register through Social Security, either online, by phone, or in person at a local office. Most people register during their 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 register later, but you may pay a higher premium for the rest of your life.

The registration process itself takes about 10 to 15 minutes if you do it online, or longer if you call or visit an office. You will need your Social Security number, birth date, and citizenship or immigration status. If you are already receiving Social Security benefits, much of this information is already on file, which speeds things up.

Part B is not automatic. Even if you sign up for Medicare Part A (hospital insurance), you must register for Part B separately. Many people assume Part B starts on its own — it does not. If you do not register during your Initial Enrollment Period and you do not have coverage from an employer or union, you will face a permanent penalty added to your monthly premium.

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.
  • You register through Social Security online at ssa.gov, by calling 1-800-772-1213, or at your local Social Security office.
  • Part B does not start automatically even if you have Part A, so you must register separately or face a permanent premium penalty.
  • If you have health coverage through your employer or union when you turn 65, you may be able to delay Part B registration without penalty.
  • Your Part B coverage begins on the first day of the month after you register, or on the first day of the month you turn 65 if you register during your Initial Enrollment Period.

Three Ways to Register: Online, Phone, or In Person

Online registration is the fastest route. Go to ssa.gov, click "Create a my Social Security account" if you do not have one, then log in and select the option to register for Medicare. You will answer questions about your citizenship, income, and current coverage. The system will confirm your information and tell you when Part B coverage begins. You should receive a confirmation email within a few minutes.

Phone registration takes longer but requires no computer. Call Social Security at 1-800-772-1213. Have your Social Security number, birth date, and information about any current health coverage ready. The representative will walk you through the same questions as the online form. The call usually takes 15 to 30 minutes. Ask for a confirmation number before you hang up.

In-person registration at your local Social Security office is an option if you prefer to speak face-to-face or if you do not have internet access. Find your nearest office at ssa.gov/locator. Bring your Social Security card, birth certificate, and proof of citizenship (passport, naturalization papers, or state ID). Bring any documents showing current health coverage if you have it. Wait times vary; some offices take walk-ins, others require an appointment. Call ahead to check.

Documents You Need Before You Register

Gather these items before you start, whether you register online, by phone, or in person. You will need your Social Security number, which is on your Social Security card. You will also need proof of U.S. citizenship or legal residency. A U.S. passport, naturalization certificate, or state driver's license usually works. If you were born outside the U.S., bring your green card or other immigration documents.

Have your birth date and current mailing address ready. If you have moved recently, update your address with Social Security before you register for Part B, or do it at the same time. If you have health coverage through an employer, a union, or a spouse's employer, have that information available — the name of the employer or plan, and whether you are still working. This matters because it affects whether you can delay Part B without penalty.

You do not need to bring Medicare documents or your Part A card. Social Security will look up whether you have Part A on file. If you do not have Part A yet, you can register for both Part A and Part B at the same time.

What Happens If You Miss Your Initial Enrollment Period

If you do not register during your seven-month Initial Enrollment Period, you can still register later during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage begins July 1 of that year. This means if you miss your Initial Enrollment Period and register in February, you will have a gap in coverage from when you turned 65 until July 1.

More important: if you register late without a valid reason, Social Security will add a permanent penalty to your Part B premium. The penalty is 10 percent for each year you delayed. If you were supposed to register at 65 but did not register until age 68, you pay an extra 30 percent on your premium for life. This penalty does not go away.

There is one major exception: if you had creditable coverage through an employer or union when you turned 65, you can delay Part B without penalty. Creditable coverage means health insurance as good as or better than Medicare. When you leave that job or that coverage ends, you have eight months to register for Part B without penalty. You will need a letter from your employer or plan stating the coverage was creditable. Keep this letter — you may need to show it to Social Security.

When Your Part B Coverage Starts

If you register during your Initial Enrollment Period (the seven months around your 65th birthday), your Part B coverage begins on the first day of the month you turn 65. This is true even if you register in the month after you turn 65. For example, if you turn 65 on June 15 and register in July, your coverage still starts June 1.

If you register after your Initial Enrollment Period ends, your coverage begins on the first day of the month after you register. If you register on March 15, coverage starts April 1. If you register on April 1, coverage starts May 1. This is why registering early matters — the sooner you register, the sooner you are covered.

You will receive your Medicare card in the mail within two to four weeks of registering. Your card will show your Medicare number and which parts of Medicare you have. Do not wait for the card to use your coverage — your coverage begins on the date Social Security tells you, even if the card has not arrived yet. If you need proof of coverage before the card arrives, you can print a temporary notice from your my Social Security account.

Your Part B Premium and When Payments Start

Most people pay a monthly Part B premium that is deducted from their Social Security check. If you are not yet receiving Social Security, you will receive a bill in the mail. The standard premium amount changes each year; Social Security announces the new amount in October for the following year. Your actual premium may be higher or lower depending on your income.

If your income was above a certain level two years ago, you will pay an Income-Related Monthly Adjustment Amount (IRMAA) on top of the standard premium. Social Security uses your tax return from two years before to calculate this. For example, in 2024, Social Security looks at your 2022 income. If your income drops significantly — because you retired, had a major loss, or had a life change — you can ask Social Security to recalculate your IRMAA.

Your first premium payment is usually due in the month your coverage begins. If you are having your premium deducted from Social Security, the deduction starts with your first check after coverage begins. If you are receiving a bill, pay it by the due date shown on the bill to avoid a late fee.

Frequently Asked Questions

Do I have to register for Part B if I am still working?

Not if you have health coverage through your job or your spouse's job. You can delay Part B without penalty as long as you have creditable coverage. When you leave that job or the coverage ends, you have eight months to register. Get a letter from your employer stating your coverage was creditable, and keep it.

What if I registered for Part A but not Part B?

You can register for Part B anytime through Social Security using the same methods — online, phone, or in person. If you are past your Initial Enrollment Period, you will pay a permanent penalty unless you had creditable coverage through an employer. Register as soon as you realize the gap.

Can I register for Part B before I turn 65?

Yes. Your Initial Enrollment Period starts three months before the month you turn 65. You can register online, by phone, or in person during this time. Registering early ensures your coverage starts on the first day of the month you turn 65.

What if I move to a different state after I register?

Your Part B coverage follows you. Update your address with Social Security so your mail and bills go to the right place. You do not need to re-register or do anything else. Your Medicare number and coverage stay the same.

Can I cancel Part B after I register?

Yes, but only during the General Enrollment Period (January 1 to March 31). If you cancel, your coverage ends June 30. If you want Part B back later, you will face a permanent penalty unless you had creditable coverage. Talk to Social Security before you cancel to understand the long-term cost.