If you are enrolling during a Special Enrollment Period (SEP) due to loss of employer coverage, you will need to attach the ...

If you’re applying during an SEP, then you will need to submit an additional form along with CMS-40b. This additional form is CMS-L564, and you must fill it out and include it with your application.

From there, you can enroll in Part B by completing these forms: CMS-40B (Application for Enrollment in Medicare – Part B [Medical Insurance]) and CMS-L564 (Request for Employment Information).