Enrolling in Medicare Part B if you already have Part A

Already Enrolled in Medicare

If you are already enrolled in Medicare Part A and you want to enroll in Part B, please complete form CMS-40B, Application for Enrollment in Medicare – Part B (medical insurance). If you are applying for Medicare Part B due to a loss of employment or group health coverage, you will also need to complete form CMS-L564, Request for Employment Information.

You have three options to submit your enrollment request under the Special Enrollment Period. 
You can do one of the following:

1. Go to “Apply Online for Medicare Part B During a Special Enrollment Period” and complete CMS-40B and CMS-L564. Then upload your evidence of Group Health Plan or Large Group Health Plan.
2. Fax your forms to 1-833-914-2016.
3. Mail your CMS-40B, CMS-L564, and evidence to your local Social Security field office.

Note: When completing the CMS-L564:

• State, “I want Part B coverage to begin (MM/YY)” in the remarks section of the CMS-40B form or online application.
• If your employer is unable to complete Section B, please complete that portion as best as you can on behalf of your employer without your employer’s signature.
• Also submit one of the following forms of secondary evidence:
  • Income tax returns that show health insurance premiums paid.
  • W-2s reflecting pre-tax medical contributions.
  • Pay stubs that reflect health insurance premium deductions.
  • Health insurance cards with a policy effective date.
  • Explanations of benefits paid by the GHP or LGHP.
  • Statements or receipts that reflect payment of health insurance premiums.

Source: https://www.ssa.gov/benefits/medicare/