When and how to sign up for Part B coverage

You enroll in Medicare Part B by contacting Social Security, Medicare, or your insurance agent during your Initial Enrollment Period — the seven-calendar-month window that starts three months before the month you turn 65. You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, by visiting your local Social Security office, or through a licensed insurance agent. Most people are automatically enrolled in Part B when they turn 65 if they are already receiving Social Security benefits, but you should verify this and understand what Part B costs before coverage begins.

Part B is optional, not automatic for everyone. If you delay enrollment without a valid reason, you may pay a permanent penalty on your monthly premium. The penalty is 10 percent of the standard Part B premium for each full year you could have had Part B but did not sign up. That penalty stays with you for life, so timing matters.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, at a Social Security office, or through a licensed insurance agent.
  • If you are already receiving Social Security at 65, you are usually enrolled automatically, but you should confirm this and review your coverage.
  • Delaying enrollment without a may have access to reason results in a permanent 10 percent monthly premium penalty for each year you wait.
  • Part B has a monthly premium (the amount varies by income and changes yearly) plus a yearly deductible and coinsurance costs when you use services.

Your seven-month Initial Enrollment Period explained

The Initial Enrollment Period is the easiest time to sign up for Part B without penalty. It begins three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, your window opens in March and closes in September. You can enroll at any point during this window; you do not have to wait until the month you turn 65.

Enrolling early in this period gives you time to resolve any paperwork issues before your coverage date. If you enroll in the month you turn 65, coverage typically starts on the first day of that month. If you enroll after that month, your coverage start date moves forward one month for each month you delay. Enrolling in July means coverage starts August 1; enrolling in August means coverage starts September 1.

How to enroll: four ways to sign up

Online at Medicare.gov: Go to Medicare.gov, sign in with your username and password (or create an account), and follow the prompts to enroll in Part B. This is the fastest method if you have your Social Security number and basic information ready. You will receive confirmation when ready.

By phone: Call 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security number, date of birth, and current address ready. The call usually takes 15 to 20 minutes.

At a Social Security office: Visit your local Social Security office in person. You can find the nearest office at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship or legal residency, and proof of age. Processing in person takes about 30 minutes.

Through a licensed insurance agent: An agent who sells Medicare plans can help you enroll in Part B at the same time you choose a supplemental or Medicare Advantage plan. Agents do not charge you a fee; they are paid by Medicare. This route works well if you want to coordinate all your coverage decisions at once.

Automatic enrollment and what to do if you are already signed up

If you are already receiving Social Security benefits when you turn 65, Medicare automatically enrolls you in Part A (hospital insurance) and Part B. You will receive a Medicare card in the mail about two weeks before your 65th birthday. Check it for accuracy — verify your name, date of birth, and Social Security number.

If you do not want Part B, you must decline it in writing. Contact Medicare at 1-800-MEDICARE or visit your local Social Security office with a signed letter stating you want to decline Part B coverage. You have until the end of the month in which you turn 65 to decline. If you decline and later change your mind, you can enroll during the General Enrollment Period (January 1 to March 31 each year), but you will owe the late enrollment penalty unless you have a may have access to reason for the delay.

If you are not yet receiving Social Security at 65, you are not automatically enrolled in Part B. You must sign up yourself during your Initial Enrollment Period to avoid the penalty.

What Part B costs and when you start paying

Part B has three costs: a monthly premium, a yearly deductible, and coinsurance. The standard monthly premium in 2024 is $164.90 for most people, but the amount changes each year and is higher for individuals with income above a certain threshold. You pay the premium whether you use services or not.

The yearly deductible (the amount you pay out of pocket before Part B starts to pay) is $240 in 2024. After you meet the deductible, you typically pay 20 percent coinsurance for most services — Medicare pays 80 percent. These amounts change yearly, so check Medicare.gov in the fall for the next year's costs.

Your first premium payment is usually due on the first day of the month your coverage starts. If you enroll online or by phone, Medicare will tell you the payment method and due date. If you enroll in person, ask the representative when and how to pay.

Special situations: exceptions to the Initial Enrollment Period

If you are still working at 65 and have health insurance through your employer, you may be able to delay Part B enrollment without penalty. This is called creditable coverage. You must have group health insurance (through your own job or a spouse's job) to may have access to. Once you leave that job or lose the coverage, you have eight months to enroll in Part B without penalty. You will need to provide proof of the employer coverage when you enroll.

If you miss your Initial Enrollment Period and do not have creditable coverage, you can still enroll during the General Enrollment Period (January 1 to March 31 each year). Coverage starts July 1 of that year. You will owe the late enrollment penalty unless you have a may have access to reason — creditable coverage is the most common one. The penalty is 10 percent of the standard premium for each full year you could have had Part B but did not.

If you are a federal employee or railroad retiree, your enrollment rules may differ. Contact your benefits administrator or the Office of Personnel Management at 1-888-767-6738 for guidance specific to your situation.

After you enroll: what happens next

Once you enroll, Medicare sends you a Medicare card by mail. The card shows your Medicare number, the date your coverage starts, and which parts of Medicare you have. Keep this card with you and show it to doctors, hospitals, and pharmacies. If you do not receive your card within two weeks of your coverage start date, call 1-800-MEDICARE.

Before your coverage begins, review your doctor and hospital options. If you have a preferred doctor, check whether they accept Medicare. You can search for providers at Medicare.gov under "Care Provider Search." If your current doctor does not accept Medicare, you will need to find a new one or pay out of pocket.

Part B does not cover everything. It covers doctor visits, outpatient services, and some preventive care, but it does not cover dental, vision, hearing aids, or long-term care. Many people add a Medigap (supplemental) plan or a Medicare Advantage plan to cover gaps. You have 63 days from the date your Part B coverage starts to enroll in a Medigap plan without medical underwriting — meaning the insurance company cannot deny you or charge more based on your health history.

Frequently Asked Questions

What if I turn 65 but am not yet receiving Social Security?

You are not automatically enrolled in Part B. You must contact Medicare yourself during your Initial Enrollment Period (three months before to three months after your 65th birthday) to sign up. If you delay beyond this window without creditable coverage, you will owe a permanent late enrollment penalty.

Can I enroll in Part B before I turn 65?

Yes. Your Initial Enrollment Period starts three months before the month you turn 65. You can enroll as early as that first month. Coverage will not start until the month you turn 65 or later, depending on when you enroll, but signing up early gives you time to handle any paperwork issues.

What if I miss my Initial Enrollment Period?

You can enroll during the General Enrollment Period (January 1 to March 31 each year), and coverage starts July 1. You will owe a permanent 10 percent monthly premium penalty for each full year you delayed, unless you had creditable coverage through an employer or are a federal employee with special rules.

Do I have to enroll in Part B if I am still working?

You can delay Part B if you have group health insurance through your current job or your spouse's current job. Once you leave that job or lose the coverage, you have eight months to enroll without penalty. You will need to provide proof of the employer coverage when you sign up.

Can I change my mind after I enroll in Part B?

You can decline Part B only during your Initial Enrollment Period or within the first three months of coverage. After that, you can only drop Part B during the General Enrollment Period (January 1 to March 31), and coverage ends June 30. If you drop and re-enroll later, you will owe the late enrollment penalty unless you have a may have access to reason.