If you're over 65 and leaving employment or ending your employer/spouse's group health plan, you'll need to complete two forms to enroll in Medicare Part B using the Special Enrollment Period (SEP).
Note: If you already have both Medicare Part A and Part B, no further action is needed at Social Security.
Two required forms
Form 1: CMS-40B (you complete and sign)
- Who fills it out: you (the Medicare beneficiary)
- Remarks section: enter your requested Medicare start date
- Start date format: always the first day of a month (April 1, 2027 or May 1, 2027)
- Timing: you can apply up to 90 days before your requested effective date
Form 2: CMS-L564 (employer completes and signs)
- Who fills it out: a representative from your employer
- Purpose: confirms your group health coverage details
Important: For couples, use separate forms for each person.
How to apply
Step 1: Have both forms completed and signed before applying
Step 2: Apply for Medicare online at ssa.gov/benefits/medicare
- Be sure to apply for both Part A and Part B
- You can now complete this process entirely online (it used to require an office visit or mail)
Step 3: Submit your two completed forms
How to submit your forms
The best option is to upload both forms when you apply online. You can also bring them to your local Social Security office in person, or mail or fax them to that office.
Important notes
- Phone contact: Social Security may call you after you apply online. Since employees may work from home, your caller ID might not show "Social Security." For security, ask the caller to confirm the date you applied online.
- Questions: call Social Security at 800-772-1213
This process is for enrolling in Medicare Part B after your Initial Enrollment Period (the 7 months around your 65th birthday month) when you've been covered by employer/union group insurance since age 65.