Form CMS-40B, Application for Enrollment in Medicare Part B (Medical Insurance)

What is CMS-40B?

CMS-40B is the Request for Enrollment in Medicare Part B (Medical Insurance), issued by the Centers for Medicare & Medicaid Services (CMS).

It is for people who already have premium-free Medicare Part A and want to sign up for Part B (Medical Insurance) during an applicable enrollment period.

If you do not have Part A, the instructions say not to complete this application and to contact Social Security to apply for Medicare for the first time.

How Social Security accepts Form CMS-40B

The blank instructs applicants to mail or fax their completed, signed form to their local Social Security office; the CMS form page also lists in-person submission.

SSA offers an online application for people age 65 or older with Part A when ending an employer group health plan during a Special Enrollment Period.

For applicants directed to complete Section 2 item 3, the form says to have their employer complete CMS-L564 and return it with the application.

If your employer cannot complete Section B, Social Security says to complete it as best you can without the employer's signature and to send other proof of coverage.

If the form is signed by mark (X), a witness who knows the person applying must also sign.

The blank on this page

The blank is marked CMS-40B (07/2025).

You can fill in this blank in the PDFLiner editor.