Form CMS-40B: how to fill it out, with a filled example
CMS-40BEd. 07/2025
Form CMS-40B, "Request for Enrollment in Medicare Part B," is how you add Part B when you already have Part A. If you worked past 65, you send it with Form CMS-L564 to sign up without a penalty.
What this form does
Who uses the CMS-40B
- You worked past 65 with health coverage from your job or your spouse's job, and that job or coverage is ending. Send it with the CMS-L564 in your 8-month Special Enrollment Period.
- You missed your window and are signing up in the General Enrollment Period, January 1 to March 31.
You must already have Part A. No Part A? Apply for Medicare through Social Security instead.
How to fill out Form CMS-40B, step by step
The example follows Walt, whose job and coverage ended in July 2026. He applied in early August. Yellow fields are the ones people get wrong most.
Section 1: Basic information
Section 2: Enrollment in Medicare Part B
Choose your coverage start date
If you apply while you are still covered by your job, or in the first full month after that coverage ends, you choose when Part B starts: the first day of the month you enroll, or the first day of any of the next 3 months.
Don't leave a gap
Section 3: Signature
Sign and date it. A witness is only needed if you sign with an X. Unsigned forms are the most common reason one comes back.
Check before you send it
- Your Medicare number and name match your card.
- The end dates in Section 2 match the CMS-L564.
- You ticked a start date.
- You signed and dated it.
- You kept a copy or a photo of every page.
How to send Form CMS-40B
- Online (fastest)Use Social Security's Part B only page. You answer these same questions on screen, sign electronically, and upload your CMS-L564 or other proof.
- By faxFax the CMS-40B and CMS-L564 to your local Social Security office (find it with the office locator). Keep the fax confirmation sheet.
- By mailMail them to your local office, by certified mail with a return receipt, at least 3 weeks before your deadline.
No letter after 30 days? Contact your local office with your confirmation in front of you. Not sure of your deadline? Use the 8-month deadline calculator. Worried you're already late? Check the Part B penalty calculator.
One full year late adds $20.29 a month to your Part B bill in 2026, for life. The kit costs $39 once.
Filled-in examples of Forms CMS-40B and CMS-L564, plus a plan for when your old employer is slow, gone, or won't sign.
- Filled CMS-40B example
- Filled CMS-L564 example for your employer
- If your employer won't sign or is gone
- 8-month deadline worksheet
- Plus 3 free bonuses, including the Letter to Your Employer's HR
Secure checkout by Gumroad · Visa · Mastercard · Amex · PayPal
- Secure checkout by Gumroad
- Instant PDF download
- Checked against SSA.gov & CMS.gov
- 14-day money-back
Retiring after 65? Get both kits for $69 instead of $88. Save $19 with the bundle
The official forms are free from ssa.gov and cms.gov. The kit is the help filling them in and proving your case. See everything inside
Questions people ask
Where do I get Form CMS-40B?
It's free on cms.gov. Search for "CMS-40B". You can also skip the paper form and apply online on Social Security's Part B only page, which asks the same questions.
Can I use the CMS-40B if I don't have Part A?
No. The CMS-40B is only for people who already have Part A. If you have neither, apply for Medicare (Part A and Part B) through Social Security instead.
Do I send the CMS-40B with the CMS-L564?
Yes, if you are signing up in a Special Enrollment Period because of job coverage. The CMS-40B is your request; the CMS-L564 (or other proof) shows you qualify.
How long does it take?
It varies by office. Keep proof of the date you applied. If you have no letter after about 30 days, contact your local Social Security office.
Can I use the CMS-40B in the General Enrollment Period?
Yes. From January 1 to March 31 anyone can sign up for Part B with the CMS-40B. Part B then starts the month after you sign up, and a late penalty may apply.
What if I don't sign it?
An unsigned form is the most common reason it comes back. Sign and date it. A witness is only needed if you sign with an X.