CENTERS FOR MEDICARE & MEDICAID SERVICES
Medicare Part B Enrollment Request (Form CMS-40B)
Ask Social Security to add Medicare Part B when the applicant already has Part A.
What is CMS-40B used for?
Form CMS-40B is the official request for someone who already has Medicare Part A and wants to sign up for Medicare Part B. The walkthrough routes the applicant through the enrollment window, coverage history, proof, and print-sign steps that apply to the current 07/2025 form.
Produce a current CMS-40B (07/2025) filled PDF ready for the applicant to print, sign, attach required evidence, and mail or fax to the local Social Security office.
Do not use CMS-40B if the applicant does not already have Medicare Part A or is outside the enrollment windows described in the official instructions.
Time, difficulty & who this form is for
Average time
10-15 minutes
Difficulty
moderate
Best for
People who already have Medicare Part A and are ready to request Medicare Part B during an Initial, General, or Special Enrollment Period.
What do I need before I start?
- The applicant's Medicare card and Medicare number
- Mailing address, phone number, and email address
- Employer or union coverage dates, if using the job coverage path
- CMS-L564 from the employer for the job coverage path
- Proof or documentation if an employer, insurer, or other entity required Part B enrollment
How the walkthrough is organized
Path check
Confirm the applicant already has Part A and is using a valid Part B enrollment window.
Basic information
Collect Medicare number, name, mailing address, phone number, and email address.
Coverage history
Route employer, union, or nonprofit volunteer coverage questions and dates only when they apply.
Required enrollment proof
Capture the explanation and proof reminder only when another entity asked or required Part B enrollment.
Coverage start choice
For the job coverage path, choose the printed coverage start option and collect the month/year only for the delayed start choice.
Print-sign handoff
Prepare the applicant signature date, witness lane when needed, attachments, and local Social Security office submission step.
What happens after I complete it?
Answer the questions, review your document, then follow its official signing and delivery instructions. Downloading does not submit the form.
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