Form CMS-40B Medicare Part B Enrollment Form (2025): Edit Online Free & Download PDF
Medicare Part B Enrollment Form: Request for Enrollment in Medicare Part B (Medical Insurance)
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Form CMS-40B in short
Form CMS-40B is how you sign up for Medicare Part B (Medical Insurance) when you already have Part A. You use it during your Initial Enrollment Period, the General Enrollment Period, or a Special Enrollment Period. If you do not have Part A yet, the form says not to use it and to contact Social Security instead.
| Issued by | Centers for Medicare & Medicaid Services (CMS), U.S. Department of Health and Human Services |
|---|---|
| Current version | CMS-40B (07/2025) (checked 2026-10-25) |
| Who fills it in | People who already have Medicare Part A and want to add Part B. If you are using a Special Enrollment Period based on job coverage, your employer also completes Form CMS-L564. |
| Who receives it | Your local Social Security office. Social Security handles Medicare enrollment. |
| Where to send it | The form says to mail or fax the completed, signed form to your local Social Security office (find it at SSA.gov/locator). CMS's form page says you can also visit the office in person. Medicare.gov says that for the job-based Special Enrollment Period you can also sign up online at SSA.gov if you already have Part A. |
| Deadline | It depends on your enrollment period. Medicare.gov says the Initial Enrollment Period lasts 7 months around your 65th birthday, the General Enrollment Period runs January 1 to March 31 each year, and the job-based Special Enrollment Period ends 8 months after the job or the group coverage ends, whichever is first. |
| Fee | No fee to file. The form notes that if you sign up for Part B you pay premiums for every month you have the coverage. |
| Official links | Official page · Official PDF |
What changed
The current edition is dated 07/2025 on the form. CMS did not publish a list of changes.
How to fill out Form CMS-40B, line by line
| Section 1, items 1 and 2 | Medicare Number and name Use the Medicare Number from your Medicare card, then your first, middle and last name and any suffix. |
| Section 1, items 3 to 5 | Address, phone and email Your mailing address and phone number. The form says all fields are required unless marked otherwise. |
| Section 2, items 1 and 2 | Employer or volunteer coverage Answer whether you had employer or union group health coverage since turning 65, or coverage as an international volunteer for a non-profit. |
| Section 2, item 3 | Work and coverage dates Enter start and end dates (mm/yyyy) for the job, any volunteer work outside the U.S., and the health coverage. Have your employer fill out Form CMS-L564 and send it with this form. |
| Section 2, item 4 | Asked to enroll by someone else Say whether an employer, insurer or other entity asked or required you to enroll in Part B, and explain with proof if yes. |
| Section 2, coverage start date | When Part B starts If you enroll while still covered by a job-based group plan, or in the first full month after, you can pick the first of the month you enroll or one of the next 3 months. |
| Section 3, items 1 to 5 | Signatures Sign and date. If you sign with an X, a witness who knows you prints their name, signs and dates. |
Common mistakes to avoid
- Using it when you do not have Part A yet. The form says to contact Social Security to apply for Medicare for the first time.
- Leaving out Form CMS-L564 when you use the job-based Special Enrollment Period. The form asks your employer to complete it and return it with your application.
- Mailing it to CMS in Baltimore. The address in the Paperwork Reduction Act notice is only for comments; send the form to your local Social Security office.
- Missing the 8-month window after job or group coverage ends. Medicare.gov says getting COBRA does not change when this window ends.
- Entering dates in the wrong format. Section 2 uses mm/yyyy and signature dates use mm/dd/yyyy.
- Signing with an X without a witness signature.
Questions about Form CMS-40B
Who should use Form CMS-40B?
People who already have Medicare Part A and want to sign up for Part B. If you do not have Part A, the form says to contact Social Security instead.
Where do I send Form CMS-40B?
Mail or fax it to your local Social Security office. CMS says you can also bring it in person. Find your office at SSA.gov/locator.
Do I need Form CMS-L564 too?
If you are signing up during a Special Enrollment Period based on job coverage, yes. The form asks you to have your employer fill out CMS-L564 and return it with your application.
When does Part B coverage start?
Medicare.gov says it generally starts the month after you sign up. If you sign up while still working, or in the first full month after employer coverage ends, you can ask to delay the start by up to 3 months.
Can I sign up for Part B online instead?
Medicare.gov says that if you already have Part A and qualify for the job-based Special Enrollment Period, you can go to SSA.gov to sign up online.
Does COBRA count as employer coverage?
No. Medicare.gov says COBRA is not group health plan coverage and does not change when the Special Enrollment Period ends.
Tools for this form
Sources
Checked against the official sources on 2026-10-25. PDF Editor Hub is not affiliated with the Centers for Medicare & Medicaid Services or any government agency. This page is general information, not legal or tax advice.
- https://www.cms.gov/medicare/cms-forms/cms-forms/downloads/cms40b-e.pdf
- https://www.cms.gov/medicare/cms-forms/cms-forms/cms-forms-items/cms017339
- https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start
- https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-can-i-sign-up-for-medicare