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How do I sign up for Medicare Part B if I already have Part A?

If you are already enrolled in Medicare Part A and you would like to enroll in Part B, please complete form CMS-40B, Application for Enrollment in Medicare – Part B (Medical Insurance).

If you are already enrolled in Medicare Part A and you would like 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 may use one of the following options to submit your enrollment request under the Special Enrollment Period:

  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 or mail your CMS-40B, CMS-L564, and secondary evidence to your local Social Security office (see list of secondary evidence below).

Note: When completing the forms CMS 40B and 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.