When and how to sign up for Part B

You sign up for Medicare 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 will pay a permanent penalty on your monthly premium unless you have a valid reason for the delay.

To sign up, you have three routes: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. Online is fastest — you can complete it in about 15 minutes if you have your Social Security number and birth date ready. The phone line has wait times but a representative will walk you through each step. Social Security offices require an appointment, which you can book online at ssa.gov.

You do not need to sign up for Part B if you are still working and have health insurance through your employer or your spouse's employer. In that case, you can delay Part B without penalty as long as you sign up within eight months of losing that coverage or retiring, whichever comes first.

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 — and missing it triggers a permanent premium penalty.
  • You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office, and online applications usually process fastest.
  • If you have employer health insurance when you turn 65, you can delay Part B without penalty as long as you sign up within eight months of losing that coverage.
  • Part B covers doctor visits, outpatient care, and some preventive services, and requires a monthly premium that changes each year.

What Part B actually covers

Medicare Part B is medical insurance that covers doctor visits, outpatient hospital services, diagnostic tests, and some preventive care like cancer screenings and vaccinations. It does not cover hospital stays (that is Part A), prescription drugs (that is Part D), or long-term care. Most people need both Part A and Part B to have basic coverage.

When you use a Part B service, Medicare pays its share and you pay the rest — usually a copay or coinsurance. You also pay an annual deductible before Medicare starts paying. The exact amounts change each year; for 2024, the Part B deductible is $240 and the monthly premium ranges from about $164 to $560 depending on your income, but these figures vary annually.

Part B is optional, but most people sign up because the penalty for not signing up when you should have is steep — your premium increases by 10 percent for each year you delay past your Initial Enrollment Period. That penalty stays with you for life.

Documents and information you will need

To sign up, have these items ready: your Social Security number, your date of birth, your citizenship or immigration status, and information about any current health insurance you have. If you are signing up by phone or in person, you may also be asked about your income, though this is mainly used to calculate any premium reductions you might receive.

If you are explore because you are losing employer coverage, gather the date that coverage ends and the name of your employer or your spouse's employer. If you missed your Initial Enrollment Period and believe you have a valid reason for the delay — such as a serious illness, a move, or a change in citizenship status — have documentation of that reason ready. Medicare calls these "exceptional circumstances," and proving one can waive the penalty.

You do not need to bring original documents to sign up online or by phone. If you explore in person at a Social Security office, bring your Social Security card and a photo ID, though staff can often verify your information electronically without seeing them.

What happens after you sign up

Once you submit your process, Medicare processes it and sends you a confirmation letter by mail within two to four weeks. This letter includes your Medicare number, your Part B effective date, and information about your premium. Your Medicare card arrives separately, usually within two weeks of approval.

Your Part B coverage typically starts on the first day of the month after you sign up, though if you sign up during your Initial Enrollment Period, it may start earlier. Check your confirmation letter for the exact date. Your first premium payment is usually deducted from your Social Security check automatically, or you receive a bill if you are not yet receiving Social Security.

Once your coverage is active, you can see any doctor who accepts Medicare. You do not need to choose a primary care doctor for Part B the way you would for a Medicare Advantage plan. However, some doctors do not accept Medicare patients, so it is worth calling ahead to confirm before your first appointment.

If you missed your enrollment important date

If you did not sign up during your Initial Enrollment Period and you are now past age 65, you can still sign up during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage begins July 1 of that year. However, you will pay a 10 percent premium penalty for each year you were may be able to access but did not sign up, and that penalty is permanent.

There are exceptions. If you were covered by an employer health plan when you turned 65, you have eight months after that coverage ends to sign up without penalty. If you were not a U.S. citizen or permanent resident when you turned 65, the clock starts when you become one. If you can document that you missed the important date because of a serious illness, a move, or a change in your life circumstances, you may be able to request a waiver of the penalty.

To request a penalty waiver, call 1-800-MEDICARE and ask to speak with a representative about "exceptional circumstances." Have documentation ready — a hospital discharge summary, a lease showing you moved, or a letter from your employer confirming the end date of coverage. Medicare reviews these requests individually and does not always approve them, but it is worth asking if your situation was genuinely beyond your control.

Part B costs and how they work

Part B has three costs: a monthly premium, an annual deductible, and coinsurance or copays when you use services. The monthly premium is income-based, meaning higher earners pay more. Most people pay the standard amount, but if your income is above a certain threshold (which changes each year), you pay a higher premium. This is called Income-Related Monthly Adjustment Amount, or IRMAA.

The annual deductible is the amount you pay out of pocket before Medicare starts covering services. Once you meet the deductible, you typically pay 20 percent of the cost of most services, and Medicare pays 80 percent. Some preventive services, like annual wellness visits and cancer screenings, have no copay or coinsurance.

If you have limited income, you may be able to get help paying Part B premiums through a program called Medicaid or the Medicare Savings Program. These are run by your state, not by Medicare itself. To learn whether you may have access to, contact your state Medicaid office or call 1-800-MEDICARE for a referral.

Frequently Asked Questions

Can I sign up for Part B after I turn 65?

Yes, but only during the General Enrollment Period (January 1 to March 31 each year), and coverage does not start until July 1. If you miss your Initial Enrollment Period, you will also pay a permanent 10 percent premium penalty for each year you were may be able to access but did not sign up. The only exception is if you had employer coverage when you turned 65 — then you have eight months after that coverage ends to sign up without penalty.

Do I have to sign up for Part B if I have employer insurance?

No. If you or your spouse are still working and have health insurance through an employer, you can delay Part B without penalty. You must sign up within eight months of losing that coverage or retiring, whichever comes first. Keep documentation of your employer coverage dates in case Medicare asks for proof later.

What if I sign up online but do not receive my Medicare card?

Medicare cards arrive by mail within two to four weeks of approval. If you have not received yours after four weeks, call 1-800-MEDICARE with your confirmation letter number. They can confirm your coverage is active and reissue your card if needed. You can use your confirmation letter as proof of coverage while you wait for the card to arrive.

Will my Part B premium change after I sign up?

Yes. Part B premiums change each year, usually in January. Medicare sends you a notice in the fall showing your new premium for the next year. If your income changes significantly — you retire, receive a large inheritance, or lose a spouse — your premium may also adjust. You can contact Social Security to report income changes and request a recalculation.

What if I cannot afford the Part B premium?

Several programs help pay Part B premiums for people with limited income. The Medicare Savings Program, run by your state, can cover your premium, deductible, and coinsurance. Medicaid may also help if your income is low enough. Call 1-800-MEDICARE and ask for a referral to your state program, or contact your state Medicaid office directly to learn what you may may have access to for.