When and how to enroll in Medicare Part B

Medicare Part B covers doctor visits, outpatient care, and medical equipment. You enroll during a specific window — usually when you turn 65 — and you do it through Social Security, not Medicare directly. Missing your window can cost you more in premiums later, so the timing matters.

You have three main enrollment periods. 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. If you miss this window but are still working and covered by your employer's health plan, you may have a different timeline. If you miss it without that coverage, you pay a permanent penalty on top of your regular premium.

The enrollment process itself is straightforward: you contact Social Security, provide basic information, and choose your coverage start date. Part B coverage typically begins the first day of the month after you enroll, though there are exceptions if you enroll in your birth month.

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 enroll through Social Security by phone, online, or in person — not through Medicare directly.
  • Part B coverage usually starts the first day of the month after you enroll, so timing your enrollment affects when coverage begins.
  • If you miss your Initial Enrollment Period without employer coverage, you will pay a higher premium for as long as you have Part B.
  • You need your Social Security number and information about any current health coverage when you enroll.

How to enroll through Social Security

Contact Social Security by phone at 1-800-772-1213 (TTY 1-800-325-0778). Have your Social Security number, date of birth, and current mailing address ready. The representative will confirm your Medicare may be able to access, ask whether you want Part B, and record your choice. The call usually takes 10 to 15 minutes.

You can also enroll online at ssa.gov if you have a my Social Security account. Log in, go to "Manage Your Benefits," and look for the Medicare enrollment option. Online enrollment is faster and you get when ready confirmation, though not all situations are available online — if yours is not, you will be directed to call or visit an office.

A third option is to visit your local Social Security office in person. Bring your Social Security card, proof of citizenship or legal residency (passport, birth certificate, or naturalization papers), and proof of your current address (utility bill, lease, or bank statement dated within the last 60 days). Offices are busiest early in the week and early in the month, so plan accordingly.

What happens after you enroll

Social Security sends you a confirmation letter within two weeks. Keep this letter — it shows your Part B start date and your premium amount. Your Medicare card arrives separately, usually within two weeks as well, though it can take up to four weeks.

Your Part B premium is deducted from your Social Security check each month, starting the month your coverage begins. The standard premium changes each year; the amount you pay depends on your income from two years prior. If your income was high, you may pay an additional amount called an Income-Related Monthly Adjustment Amount (IRMAA).

If you enrolled during your Initial Enrollment Period, your coverage starts on the first day of the month after you enroll — with one exception. If you enroll in the month you turn 65, coverage can start that same month if you enroll by the 14th. Otherwise, coverage starts the first of the following month.

If you missed your Initial Enrollment Period

You can still enroll, but the rules change. If you have current coverage through an employer or union, you may have up to eight months after that coverage ends to enroll without penalty. This is called a Special Enrollment Period. You must show proof of employer coverage — usually a letter from your employer's benefits office or your health plan documents.

If you do not have employer coverage and you missed your Initial Enrollment Period, you can enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage starts July 1. However, you will pay a permanent penalty: your monthly premium increases by 10 percent for each full year you were may be able to access but not enrolled. This penalty stays with you for life.

Contact Social Security to discuss your specific situation. Bring documentation of any coverage you had and the dates it ended. Social Security can tell you whether you may have access to for a Special Enrollment Period or whether the General Enrollment Period is your only option.

Documents you need to have ready

Before you call or visit, gather these items:

  • Your Social Security number
  • Your date of birth
  • Your current mailing address
  • Information about any current health coverage (employer plan, COBRA, Medicaid, or Veterans benefits)
  • Your citizenship or legal residency status (you will need to state it; documentation is required only if you visit an office)

If you are enrolling after your Initial Enrollment Period, also have the dates your previous coverage ended and documentation of that coverage — a letter from your employer, a copy of your health plan card, or a benefits statement.

Part B costs and what is covered

Part B has two costs: a monthly premium and an annual deductible. The monthly premium is deducted from your Social Security check. The deductible is the amount you pay out of pocket before Part B starts paying its share. Both amounts change each year.

Part B covers doctor office visits, preventive care (like annual wellness visits and screenings), outpatient surgery, mental health services, and durable medical equipment like wheelchairs and oxygen. It does not cover dental, vision, or hearing care. After you meet your deductible, you typically pay 20 percent of the cost of covered services; Medicare pays 80 percent.

Many people add Medigap (supplemental insurance) or Medicare Advantage (Part C) to reduce their out-of-pocket costs. These are separate choices you make after Part B enrollment, usually during the same enrollment period.

Common mistakes to avoid

The biggest mistake is waiting too long to enroll. Your seven-month Initial Enrollment Period sounds long, but it passes quickly. Mark your calendar three months before you turn 65 and enroll then — do not wait until the last month. If you wait and miss the important date, you cannot undo the penalty.

Do not assume your employer coverage extends your enrollment window. Some employers do, but many do not. If you are still working at 65, contact your employer's benefits office to ask whether you can delay Part B without penalty. Get the answer in writing. If the answer is yes, keep that letter; you will need it to prove you had employer coverage when you eventually enroll.

Do not confuse Part B enrollment with Medicare enrollment. You are automatically enrolled in Part A (hospital insurance) at 65 if you are receiving Social Security. Part B is separate and requires you to take action. If you do nothing, you do not get Part B.

Frequently Asked Questions

What if I am still working at 65 and have health insurance through my job?

You may be able to delay Part B without penalty. Contact your employer's benefits office and ask whether you can delay Part B while you have employer coverage. If yes, get that answer in writing. When you leave your job or lose coverage, you will have eight months to enroll in Part B without penalty. If your employer says no, enroll in Part B anyway to avoid the permanent penalty.

Can I enroll in Part B after I turn 65 if I did not enroll before?

Yes, but it depends on how long you have waited. If you missed your Initial Enrollment Period but have current employer coverage, you have up to eight months after that coverage ends. If you do not have employer coverage, you can enroll during the General Enrollment Period (January 1 through March 31), but you will pay a higher premium for life.

When does Part B coverage actually start?

Coverage usually starts the first day of the month after you enroll. The exception is if you enroll in the month you turn 65 and you enroll by the 14th — then coverage can start that same month. Ask Social Security for your specific start date when you enroll.

Do I have to take Part B if I am still working?

No, but you need to know the rules. If you have employer coverage, you can usually delay Part B without penalty. If you do not have employer coverage and you do not enroll, you will pay a permanent penalty later. Contact Social Security or your employer's benefits office to understand your specific situation.

What if I enrolled but want to cancel Part B?

You can drop Part B, but you will likely face a penalty if you enroll again later. Contact Social Security to discuss your reasons. If you are still working and have employer coverage, dropping Part B might make sense. If you are retired, dropping it usually costs you more in the long run.