UPDATED on Oct. 27, 2023. Medicare Part B is the Medical Insurance portion of Original Medicare, allowing you to use any doctor, specialist, or hospital that accepts Medicare. To enroll in Medicare Part B, you may use one of the several enrollment periods: Initial Enrollment Period, General Enrollment Period, Special Enrollment Period for people covered under current employment.
Medicare Part B is optional.
Article Contents
When to Enroll: Initial Enrollment Period
When to Enroll: General Enrollment Period
When to Enroll: Special Enrollment Period
How to Enroll in Part B
US Government Sources
When to enroll in Medicare Part B – Initial Enrollment Period
An Initial Enrollment Period (IEP) is a seven-month period that begins 3 months before you turn age 65, includes the month you turn age 65, and ends three months after that birthday. In the case of disability, it starts 3 months before your 25th month of disability and lasts also seven months. You can sign up anytime during the Initial Enrollment Period. The following chart below shows when your Medicare Part B becomes effective:
| If you enroll in this month of your initial enrollment period | Then your Medicare Part B coverage starts |
| One to three months before you reach age 65 | The month you reach age 65 |
| The month you reach age 65 | One month after the month you reach age 65 |
| One month after you reach age 65 | Two months after the month of enrollment |
| Two or three months after you reach age 65 | Three months after the month of enrollment |
When to enroll in Medicare Part B – General Enrollment Period
If you don’t enroll in Medicare Part B during your initial enrollment period, you have another chance each year to sign up during a General Enrollment Period from January 1 through March 31. Your coverage begins on July 1 of the year you enroll. However, you may need to pay a late enrollment penalty for as long as you have Part B coverage.
When to enroll in Medicare Part B – Special Enrollment Period for People Covered Under Current Employment
If you’re 65 or older and covered under a group health plan, either from you or your spouse’s current employment, you may have a Special Enrollment Period (SEP) in which to sign up for Medicare Part B. This means that you may delay enrolling in Medicare Part B without having to wait for a General Enrollment Period and paying the penalty for late enrollment.
You may
- Enroll in Medicare Part B any time while you have a group health plan based on current employment; or
- Enroll in Medicare Part B during the eight-month period that begins the month after the employment ends or the group health coverage ends, whichever happens first.
When you enroll in Medicare Part B while you’re still in the group health plan, or during the first full month when you are no longer in the plan, your coverage begins either
- On the first day of the month you enroll; or
- By your choice, on the first day of any of the following three months.
If you enroll during any of the remaining seven months of the Special Enrollment Period, your Medicare Part B coverage begins on the first day of the following month.
If you don’t enroll by the end of the eight months period, you’ll have to wait until the next general enrollment period, which begins on January 1 of the next year.
Notice that COBRA and retiree health coverage don’t count as current employer coverage.
How to enroll in Medicare Part B
Initial Enrollment: Medicare Part A and Part B
- Apply online at Social Security.
- Visit your local Social Security office.
- Call Social Security at 1-800-772-1213. TTY users should call 1-800-325-0778.
- If you worked for a railroad, call the RRB at 1-877-772-5772.
How to enroll for Part B only (assuming you already have Part A)
- Complete form CMS 40-B, Application for Enrollment in Medicare – Part B (Medical Insurance), and take or mail it to your local Social Security office. Enclose also the Form CMS-L564 “Request for Employment Information” completed by your employer if you’re signing up in a SEP. Use the Form CMS 40-B
• If you’re in your IEP and refused Part B or did not sign up when you applied for Medicare, but now want Part B.
• If you’re going to sign up for Part B during the General Enrollment Period (GEP) from January 1 – March 31 each year.
• If you refused Part B during your IEP because you had group health plan (GHP) coverage through your or your spouse’s current employment. You may sign up during your 8-month Special Enrollment Period (SEP).
US Government Sources
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