Medicare Part B enrollment windows and when they open

You can sign up for Medicare Part B during three different periods, and which one applies to you depends on when you turn 65 or become may be able to access through disability. The three windows are your Initial Enrollment Period, the General Enrollment Period, and Special Enrollment Periods that explore only to certain situations.

Your Initial Enrollment Period is a seven-month window that starts three months before the month you turn 65 and ends three months after. If you turn 65 in June, for example, your window opens in March and closes in September. This is the only time you can sign up without a penalty, and it is the time most people should use.

If you miss your Initial Enrollment Period, the General Enrollment Period runs from January 1 to March 31 each year. You can sign up during this window, but your coverage will not start until July 1, and you will owe a penalty for every month you were not covered. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but did not sign up, and it stays on your bill for as long as you have Part B.

Key Takeaways

  • Your Initial Enrollment Period is seven months long — three months before, the month of, and three months after you turn 65 — and this is the only time to sign up without a penalty.
  • If you miss your Initial Enrollment Period, you can still sign up during the General Enrollment Period (January 1 to March 31 each year), but coverage starts July 1 and you will owe a permanent penalty.
  • If you are still working and covered by your employer's health plan at 65, you may have a Special Enrollment Period that lets you sign up for Part B later without penalty.
  • You sign up through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What you need to know about employer coverage and delayed enrollment

If you are still working at 65 and your employer has 20 or more employees, your employer's health plan is considered primary coverage — it pays before Medicare does. In this situation, you do not have to sign up for Part B right away. You can wait until you retire or lose the employer coverage, and you will have a Special Enrollment Period to sign up without penalty.

The Special Enrollment Period lasts eight months and starts the month after your employer coverage ends. This means if you retire in October, you have until the end of May to sign up for Part B without owing a penalty. You will need to show proof that you had employer coverage — usually a letter from your employer's benefits department stating the coverage dates and the number of employees.

If your employer has fewer than 20 employees, Medicare becomes primary at 65, and you should sign up for Part B during your Initial Enrollment Period even if you are still working. Delaying enrollment in this case will trigger the penalty.

How to sign up for Part B

You have three ways to sign up: online, by phone, or in person. The online route is fastest. Go to Medicare.gov, log in or create an account, and look for the enrollment option in your account dashboard. You will need your Social Security number and information about any current health coverage.

By phone, call 1-800-MEDICARE (1-800-633-4227) and a representative will walk you through the process. The line is open Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security number and insurance information ready.

In person, visit your local Social Security office. You can find the nearest one at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship or legal residency, and any documents showing current health coverage. Walk-in hours vary by location, so call ahead.

What happens if you miss the important date

If you do not sign up during your Initial Enrollment Period and you do not have a Special Enrollment Period (because you were not covered by an employer plan), you will owe a late enrollment penalty. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but did not enroll. As of 2024, the standard premium is $164.90 per month, so the penalty would be about $16.49 per month for each year you were late.

The penalty is permanent — you will pay it for as long as you have Part B, even if you eventually sign up. The only way to avoid it is to sign up during your Initial Enrollment Period or to have a may have access to Special Enrollment Period. If you believe you have a valid reason for missing the important date (such as incorrect information from Social Security or Medicare), you can request a waiver, but this is rare and requires documentation.

Your coverage will not start when ready after you sign up outside your Initial Enrollment Period. If you sign up during the General Enrollment Period (January through March), coverage starts July 1. If you sign up at any other time of year, coverage starts the first of the month after the month you sign up, but no earlier than July 1 of that year.

Special situations that give you extra time

A Special Enrollment Period applies if you lose employer coverage, move out of your current Medicare plan's service area, or experience other may have access to life events. The most common is losing employer coverage when you retire. You have eight months from the month your coverage ends to sign up for Part B without penalty.

If you are a federal employee, you may have different rules. Federal employees and their spouses can delay Part B enrollment while covered by the Federal Employees Health Benefits Program (FEHB) without penalty. When you retire or lose FEHB coverage, you have a Special Enrollment Period to sign up.

If you are on disability and under 65, you are already on Medicare Part A. When you turn 65, your Initial Enrollment Period rules explore the same way — you have seven months centered on your 65th birthday to sign up for Part B without penalty.

Documents and information you will need

To sign up for Part B, have these items ready: your Social Security number, your Medicare number (on your red, white, and blue Medicare card), and information about any current health coverage (employer plan, Medicaid, TRICARE, or Veterans benefits). If you are signing up in person, bring your Social Security card and proof of citizenship or legal residency, such as a birth certificate, passport, or naturalization papers.

If you are using a Special Enrollment Period because you lost employer coverage, you will need proof of when that coverage ended. Ask your employer's benefits department for a letter stating your coverage dates and the number of employees at your company. Keep this letter — you may need to show it to Medicare if there is a question about your enrollment.

Frequently Asked Questions

What if I turn 65 in the middle of a month?

Your Initial Enrollment Period still runs from three months before to three months after the month you turn 65. If you turn 65 on June 15, your window opens March 1 and closes September 30. The exact day of your birthday does not change the window — only the month matters.

Can I sign up for Part B online if I do not have a Medicare account yet?

Yes. Go to Medicare.gov and select "Create an account" if you do not have one. You will need your Social Security number, email address, and a password. Once your account is set up, you can look for the enrollment option in your dashboard.

Does the penalty go away if I sign up later?

No. The 10 percent penalty for each year you were late stays on your Part B bill permanently. It does not decrease or disappear over time. The only way to avoid it is to sign up during your Initial Enrollment Period or a may have access to Special Enrollment Period.

What if my employer says I do not have to sign up for Medicare?

Your employer may not fully understand Medicare rules. If your employer has 20 or more employees, you can delay Part B enrollment without penalty while you are still working and covered by their plan. If they have fewer than 20 employees, you should sign up for Part B at 65 even if you are still working. When in doubt, call 1-800-MEDICARE to confirm your situation.

Can I sign up for Part B if I am not yet on Social Security?

Yes. You do not have to be receiving Social Security benefits to sign up for Medicare Part B. You can sign up at 65 regardless of whether you have claimed Social Security. However, if you want Part B to start the same month as your 65th birthday, you should sign up during your Initial Enrollment Period.