Medicare Part B enrollment windows are tied to when you turn 65 or lose other health coverage

You can enroll in Medicare Part B during three main periods: your Initial Enrollment Period (IEP), which starts three months before the month you turn 65; the General Enrollment Period (GEP), which runs January 1 to March 31 each year; or a Special Enrollment Period (SEP) if you lose employer coverage or move to a new state. The window you use depends on your age and your current insurance situation.

If you miss your IEP without a valid reason, you will pay a late enrollment penalty for as long as you have Part B. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled. This penalty does not go away, so timing matters.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before you turn 65, the month you turn 65, and three months after.
  • If you are still working and covered by your employer's health plan, you may be able to delay Part B enrollment without a penalty through a Special Enrollment Period.
  • The General Enrollment Period (January 1 to March 31) is open every year, but enrollment that month does not take effect until July 1.
  • Late enrollment penalties are permanent and equal 10 percent of the standard premium for each year you delayed, so enroll during an open window when you can.

Your Initial Enrollment Period: the seven-month window around age 65

Your Initial Enrollment Period is the easiest time to enroll in Part B. It begins three months before the month you turn 65 and ends three months after. That gives you a total of seven months to sign up without penalty.

For example, if you turn 65 in June, your IEP runs from March through September. You can enroll any time during those seven months, and your coverage will start on the first day of the month you turn 65 (or the first of the following month if you enroll after your birthday month).

You do not have to enroll in Part B during your IEP if you are still working and covered by your employer's health plan. However, you should understand the rules about delayed enrollment before you skip it—missing the window without a valid reason triggers the permanent penalty.

Delayed enrollment if you have employer coverage

If you are still working at age 65 and your employer has 20 or more employees, you can delay Part B enrollment without penalty. This is called a Special Enrollment Period based on group health plan coverage. You must enroll within eight months after your employment ends or your employer coverage stops, whichever comes first.

The key requirement is that you must be enrolled in the employer plan when you turn 65. If you drop the coverage before 65, you lose this protection and will owe the late penalty if you do not enroll during your IEP.

When you do enroll during your SEP, coverage typically starts the first of the month after you submit your enrollment. Contact Medicare or your Social Security office to confirm the exact start date for your situation.

The General Enrollment Period: January 1 to March 31 each year

If you miss your IEP, the General Enrollment Period opens every January 1 and closes March 31. You can enroll during this window, but there is a catch: coverage does not start until July 1 of that year, and you will owe the late enrollment penalty.

For example, if you turn 66 in April and missed your IEP, you could enroll during the next GEP (January 1 to March 31 of the following year). Your coverage would start July 1, and you would pay the 10 percent penalty on top of your regular premium.

The GEP exists as a safety net, but it is not a good option if you can avoid it. The gap between enrollment and coverage start, plus the permanent penalty, makes it far better to enroll during your IEP or a valid SEP.

Special Enrollment Periods for life changes

Beyond employer coverage, you may may have access to for a Special Enrollment Period if you move to a new state, lose Medicaid, or experience other may have access to events. These periods usually last two months and allow you to enroll without the late penalty.

Common may have access to events include losing employer coverage, moving out of your current Medicare Advantage plan's service area, or becoming ineligible for Medicaid. Each situation has its own rules about when the SEP starts and how long it lasts.

If you think a life change might may have access to you for an SEP, contact Medicare at 1-800-MEDICARE or visit Medicare.gov to ask. It is worth checking before you assume the late penalty applies.

How to enroll during your window

You can enroll in Part B through three channels: online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. You will need your Social Security number and information about any current health coverage.

If you are already receiving Social Security benefits, you may be enrolled in Part B automatically during your IEP. Check your Social Security statement or call to confirm. If you are not yet receiving benefits, you must enroll yourself.

Enrollment typically takes a few minutes, and you should receive a confirmation notice in the mail within two weeks. Your coverage will start on the date Medicare tells you, usually the first of a given month.

Understanding the late enrollment penalty

The late enrollment penalty applies if you do not enroll in Part B during your IEP and do not have a valid reason for the delay. The penalty is 10 percent of the standard Part B premium amount for each full 12-month period you were may be able to access but not enrolled.

The standard Part B premium changes each year. In 2024, the standard premium is $164.90 per month, but this amount varies based on your income. Your actual premium may be higher or lower. The penalty is calculated on the standard amount, not your income-adjusted amount.

Once you enroll and start paying the penalty, it stays with you for life. There is no way to remove it, even if you later move to a different state or change plans. This is why enrolling on time matters so much.

Frequently Asked Questions

What happens if I enroll in Part B after my IEP ends but before I turn 66?

You will have to wait for the next General Enrollment Period (January 1 to March 31) to enroll, and your coverage will not start until July 1. You will also owe the late enrollment penalty. There is no enrollment window between the end of your IEP and the start of the next GEP unless you have a may have access to life event.

Can I enroll in Part B if I am still working past age 65?

Yes. If your employer has 20 or more employees and you are covered by their health plan, you can delay Part B without penalty. You must enroll within eight months after you stop working or lose the employer coverage. If your employer has fewer than 20 employees, you should enroll during your IEP to avoid the penalty.

Do I have to enroll in Part B if I have a Medicare Advantage plan?

No. Medicare Advantage (Part C) includes Part B coverage, so you do not need to enroll in Part B separately. However, you must be enrolled in Original Medicare Part A and Part B to join a Medicare Advantage plan, so the enrollment still happens—it is just bundled into your Advantage plan enrollment.

What if I move to a different state after I turn 65?

Moving to a new state may trigger a Special Enrollment Period if your current Medicare Advantage plan does not serve your new location. You would have two months from the date you move to enroll in a new plan without penalty. Contact Medicare to confirm whether your move qualifies for an SEP.

Can the late enrollment penalty ever be removed?

No. The penalty is permanent and stays with you as long as you have Part B. There is no appeal process or waiver, even if you had a good reason for the delay. This is why it is important to enroll during your IEP or a valid Special Enrollment Period.