CMS-40B fax number: where to fax Medicare Part B enrollment

Medicare Part B enrollment fax (CMS-40B and CMS-L564)

Checked against ssa.gov on November 11, 2026

Fax CMS-40B (and CMS-L564 for a special enrollment period) to your local Social Security office; find its fax in SSA’s office locator. Ignore the central number 1-833-914-2016 you may see online: it came from a 2020 notice, and current SSA pages and the form itself say to send it to your local office.

How to fax it

Fill in and sign CMS-40B. In the remarks, write “I want Part B coverage to begin (MM/YY)”.
Special enrollment period? Add CMS-L564 with Section B completed by your employer, plus proof of your group health coverage.
Find your local office’s fax at ssa.gov/locator (Office information › Contact numbers › Fax).
Send it from dimefax.com/send.
Keep the delivered confirmation. Dimefax shows the date and time it went through.

Tips

You can also apply online at ssa.gov and upload the forms and evidence, or call 1-800-772-1213.

Dimefax costs 10¢ a page and you’re only charged if the fax goes through. On the web, page credits come in packs of 50 for $4.99, 100 for $9.99 or 200 for $19.99; the Dimefax iPhone app also sells 10 for $0.99. Credits you don’t use stay in your account and last as long as you fax once a year.

Where these numbers come from

Dimefax isn’t part of, or endorsed by, the Social Security Administration. We copied these numbers from ssa.gov on November 11, 2026. Agencies change their numbers: if your letter, notice or form gives a different one, use that.

Questions

What is the fax number for CMS-40B?

Your local Social Security office’s fax number, from the SSA office locator. There’s no current central number.

Is 1-833-914-2016 still the CMS-40B fax?

Current official pages don’t list it. That number came from a 2020 SSA notice; today SSA and the form say to send CMS-40B to your local office.