Medicare Part B enrollment windows and important date

You can sign up for Medicare Part B during three main periods: your Initial Enrollment Period, the General Enrollment Period, or a Special Enrollment Period if you meet certain conditions. Most people get a seven-month window that includes the month they turn 65, the three months before, and the three months after. Missing this window usually means paying a permanent penalty on your Part B premium for as long as you have Medicare.

The General Enrollment Period runs from January 1 to March 31 each year, and coverage starts July 1 of that same year. This is the fallback option if you missed your Initial Enrollment Period, but it comes with the penalty. A Special Enrollment Period may be available if you were covered by an employer health plan when you turned 65, or if you lost coverage for specific reasons — these periods have their own rules and important date.

Key Takeaways

  • Your Initial Enrollment Period is a seven-month window: three months before you turn 65, the month you turn 65, and three months after.
  • If you miss your Initial Enrollment Period and do not have a Special Enrollment Period, you can sign up during the General Enrollment Period (January 1 to March 31), but coverage does not start until July 1.
  • Delaying Part B past your Initial Enrollment Period without a may have access to reason results in a permanent 10 percent premium increase for each full year you delayed.
  • You can sign up through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • If you were working and covered by your employer's health plan at 65, you may have a Special Enrollment Period that extends eight months after you or your spouse stops working or loses coverage.

Your Initial Enrollment Period explained

Your Initial Enrollment Period is the easiest and penalty-free way to sign up for Part B. It starts 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. Social Security will send you a notice about your enrollment period roughly three months before you turn 65.

You do not have to sign up on the first day — you have the full seven months. However, if you want coverage to start on your 65th birthday, you should sign up by the end of the month you turn 65. If you sign up after that month but still within your window, coverage typically starts the first day of the following month. Signing up in the last month of your window (three months after you turn 65) means coverage starts two months later.

What happens if you miss your Initial Enrollment Period

If you do not sign up during your Initial Enrollment Period and you do not have a Special Enrollment Period, you will pay a permanent late enrollment penalty. This penalty is 10 percent of the standard Part B premium for each full 12-month period you were may be able to access but not signed up. Once you sign up, this higher premium stays with you for life — it does not go away after a certain number of years.

The penalty applies even if you were covered by another health plan during the time you delayed. The only exceptions are if you had employer coverage (which may may have access to you for a Special Enrollment Period) or if you were living outside the United States and covered by the Veterans Health Administration.

Special Enrollment Periods for employer coverage

If you were covered by a health plan through your own job or your spouse's job when you turned 65, you may have a Special Enrollment Period that protects you from the late penalty. This period lasts eight months after the coverage ends — either when you or your spouse stops working, or when the employer coverage ends for another reason. You must sign up during this eight-month window to avoid the penalty.

You will need to show proof that you had employer coverage, such as a letter from your employer or a copy of your health insurance card. Social Security or Medicare will ask for this documentation when you sign up. If your employer coverage ended before you turned 65, your Special Enrollment Period still starts from the date the coverage ended, not from your 65th birthday.

The General Enrollment Period as a backup option

The General Enrollment Period runs from January 1 to March 31 every year. Anyone can sign up during this time, regardless of whether they missed their Initial Enrollment Period. However, coverage does not start until July 1 of that year, which means there is a gap between when you sign up and when your coverage begins.

Using the General Enrollment Period also means you will pay the late enrollment penalty unless you have a may have access to reason for the delay. For example, if you missed your Initial Enrollment Period in 2023 and sign up during the January-March 2024 General Enrollment Period, your penalty will be based on the 12 months you were may be able to access but not enrolled in 2023.

How to sign up for Part B

You can sign up through three main channels. Medicare.gov has an online enrollment tool where you can create an account and submit your information. You can also call 1-800-MEDICARE (1-800-633-4227) to speak with someone who can walk you through the process — this line is available 24 hours a day, seven days a week. A third option is to visit your local Social Security office in person with your Medicare card and identification.

When you sign up, have your Social Security number, date of birth, and citizenship or immigration status ready. If you are signing up during a Special Enrollment Period, you will also need to provide proof of your employer coverage or the reason for your delayed enrollment. Processing usually takes a few weeks, and you will receive a Medicare card in the mail once your enrollment is complete.

Understanding the coverage start dates

The month your Part B coverage starts depends on when you sign up within your enrollment period. If you sign up during the month you turn 65, coverage starts on the first day of that month — even if you sign up on the last day. If you sign up in the month after you turn 65, coverage starts the first day of the following month. If you sign up in the third month after you turn 65, coverage starts two months later.

During the General Enrollment Period, coverage always starts July 1, regardless of which month you sign up. This delay is one reason why signing up during your Initial Enrollment Period is preferable — you can have coverage start right away without waiting months for it to take effect.

Frequently Asked Questions

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

Yes. Your Initial Enrollment Period starts three months before you turn 65, so you can sign up as early as then. Many people sign up a few months before their 65th birthday to may support coverage starts on time. You do not have to wait until the month you turn 65.

What if I was working past 65 and had employer health insurance?

If you were covered by your employer's health plan when you turned 65, you have a Special Enrollment Period that lasts eight months after that coverage ends. You can sign up without penalty during this window, even if it is years after you turned 65. You will need to provide proof of the employer coverage.

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

If you have coverage through your employer or your spouse's employer, you may be able to delay Part B without penalty. However, if you have other types of insurance (like individual plans or retiree coverage), you still need to sign up during your Initial Enrollment Period or face the penalty. The rules depend on the type of coverage you have.

What is the late enrollment penalty, and how much does it cost?

The late enrollment penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not signed up. For example, if you delayed for two years, your premium would be 20 percent higher. This penalty is permanent and stays on your premium for the rest of your time on Medicare.

Can I change my mind and drop Part B after I sign up?

Yes, but only during certain times. You can drop Part B during the General Enrollment Period (January 1 to March 31), and the change takes effect July 1. Outside this window, you generally cannot drop Part B unless you have employer coverage or move outside the United States. Dropping and re-enrolling later will trigger the late penalty.