Where and when to sign up for Medicare Part B

You sign up for Medicare Part B through Social Security, either online at ssa.gov, by phone at 1-800-772-1213, or in person at your local Social Security office. The timing matters: you have a seven-month window centered on your 65th birthday — three months before, the month you turn 65, and three months after. If you miss this window, you may pay a permanent penalty on your premiums unless you have a valid reason for the delay.

Most people are automatically enrolled in Part B when they turn 65 if they are already receiving Social Security benefits. You can check your enrollment status on your Social Security account at ssa.gov or by calling Social Security directly. If you were automatically enrolled and do not want Part B, you have a short window to decline it — usually the month you turn 65 plus two months after.

Key Takeaways

  • Sign up through Social Security online, by phone, or at a local office during the seven-month window around your 65th birthday.
  • Most people are automatically enrolled in Part B at 65 if they already receive Social Security, but you can decline if you have other coverage.
  • Missing the initial enrollment window can result in a permanent 10 percent penalty added to your Part B premium for each year you delay.
  • If you are still working and covered by your employer's health plan, you may be able to delay Part B without penalty — but you must tell Social Security about your work coverage.

Automatic enrollment and when it happens

If you are receiving Social Security retirement, survivor, or disability benefits before age 65, Medicare Part B enrollment happens automatically three months before you turn 65. You will receive your Medicare card in the mail about two weeks before your coverage starts on the first day of the month you turn 65. You do not need to do anything unless you want to decline Part B.

If you are not yet receiving Social Security when you turn 65, you will need to contact Social Security to enroll in Part B. This is the most common reason people miss the enrollment window — they assume Medicare will find them automatically, but it does not if they have not claimed Social Security yet.

How to enroll online, by phone, or in person

Online: Go to ssa.gov and create a my Social Security account if you do not have one. Once logged in, you can view your Medicare status and submit an enrollment request. This is the fastest method and you can do it any time of day.

By phone: Call Social Security at 1-800-772-1213. Have your Social Security number and birth certificate information ready. Representatives are available Monday through Friday, 7 a.m. to 7 p.m. local time. Wait times are usually shorter early in the morning.

In person: Visit your local Social Security office. You can find the nearest one at ssa.gov/locator. Bring your Social Security card, birth certificate, and proof of citizenship or legal residency. No appointment is required, but you may wait longer during peak hours (mid-morning and mid-month).

What happens if you miss the initial enrollment window

If you do not sign up during your seven-month enrollment window and you do not have a valid reason for the delay, you will face a late enrollment penalty. This penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled. Once added to your premium, this penalty stays for as long as you have Part B.

For example, if you turned 65 in January 2024 and did not enroll until January 2026, you would owe a penalty for two years of delay. The penalty would be added to your monthly premium permanently, even if you move to a different state or change plans later.

There are exceptions to this penalty. If you were covered by an employer or union health plan while you were working, or if your spouse was working and you were covered under their plan, you may not owe a penalty. You must tell Social Security about this coverage when you enroll, and you will need to provide proof — usually a letter from your employer's benefits department stating the dates you were covered.

Delaying Part B if you have employer coverage

If you are still working at 65 and covered by your employer's health plan, you can delay Part B without penalty. This is called creditable coverage. You do not have to enroll in Part B until you leave your job or lose the employer coverage, whichever comes first.

The key step is notifying Social Security that you have employer coverage. When you eventually enroll in Part B — whether that is at 66, 68, or later — bring documentation from your employer showing your coverage dates and that the plan is creditable. Without this documentation, Social Security may still charge you a late penalty.

If your spouse is still working and you are covered under their employer plan, the same rule applies. You can delay Part B, but you must tell Social Security about the coverage when you enroll.

What you need to bring or have ready

Whether you enroll online, by phone, or in person, you will need the same basic information:

  • Your Social Security number
  • Your date of birth
  • Your citizenship or legal residency status
  • Information about any current health coverage (employer plan, TRICARE, VA coverage, or other Medicare parts)
  • If you have employer coverage, the name of your employer and the dates you were covered

If you are enrolling in person, bring your Social Security card and birth certificate as proof of identity. If you are explore online or by phone, you will not need to mail documents unless Social Security specifically asks for them.

When your Part B coverage starts

Coverage typically begins on the first day of the month after you enroll, though the exact date depends on when you submit your enrollment request. If you enroll during your initial seven-month window, your coverage will start on the first day of the month you turn 65 or the month after, depending on when you enroll within that window.

Your Medicare card will arrive in the mail before your coverage starts. If you do not receive it within two weeks of your start date, call Social Security to request a replacement. You do not need the physical card to use your benefits — your coverage is active even if the card has not arrived yet.

Frequently Asked Questions

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

No. If you are covered by your employer's health plan, you can delay Part B without penalty. However, you must tell Social Security about your employer coverage when you eventually enroll, and you will need proof from your employer showing the dates you were covered and that the plan is creditable.

What if I turned 65 more than seven months ago and did not enroll?

You can still enroll, but you will likely owe a late enrollment penalty unless you have a valid reason for the delay (such as employer coverage). Contact Social Security to discuss your situation and provide any documentation you have about coverage during the time you were not enrolled in Part B.

Can I enroll in Part B after I decline it?

Yes, but only during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage would start July 1 of that year. You will owe a late penalty unless you have a valid reason for declining it initially.

What if Social Security says I am already enrolled but I did not sign up?

This means you were automatically enrolled because you were receiving Social Security benefits. If you do not want Part B, you have until the end of the month after you turn 65 to decline it. Contact Social Security in writing or by phone to request disenrollment.

Do I need to enroll in Part B if I have Medicare Advantage or Medigap?

Yes. Part B is required for both Medicare Advantage and Medigap plans. You must be enrolled in both Part A and Part B before you can enroll in either of these plans. Enroll in Part B through Social Security at the same time you are considering these other coverage options.