If you delayed Part B because you or your spouse had group health coverage based on current employment, Social Security may ask for CMS-40B and CMS-L564 when you are ready to enroll.

What each form does

CMS-40B requests enrollment in Medicare Part B. CMS-L564 asks the employer to confirm the dates of employment and group health coverage used to support a Special Enrollment Period.

  • Complete CMS-40B with the requested Part B effective date
  • Ask the employer to complete Section B of CMS-L564
  • Keep copies of everything submitted

When these forms are generally used

They are commonly used when someone already has Part A and wants to add Part B after delaying it because of qualifying active-employment coverage. Social Security also offers an online Part B Special Enrollment Period application for many situations.

Coordinate the effective date

Start before employer coverage ends. Confirm the last day of current coverage and the requested Part B start date so you can avoid an unintended gap.

  • Do not assume COBRA extends the Part B enrollment window
  • Confirm receipt and application status with Social Security
  • Wait for confirmed Part A and Part B dates before finalizing other coverage
Important: This article is for educational purposes and is not a complete statement of Medicare rules. Enrollment rights, costs, benefits and plan availability can vary by situation and location. Confirm current guidance before making a coverage decision.