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Quick answer: Find your two senators on senate.gov and your representative on house.gov by ZIP code, then look for a fax number on each member’s own contact page. Not every office publishes one. Put your name and full home address at the top, keep to one issue on one page, name the bill if there is one (H.R. 1234 for a House bill, S. 567 for a Senate one), and keep the confirmation when it sends.
Mail to Congress is slow. Letters to the Washington offices go through security screening first, and one House office’s own FAQ puts the delay at one to two weeks; another calls mail “the slowest method” of reaching it. A fax arrives the same day, on paper, with your signature on it, and you keep a dated record that it went through.
That makes it worth the effort when timing matters, such as a vote coming up, or when you’re sending something signed, like a form asking the office to help with a federal agency.
Work out who represents you
Everyone has two senators and one representative. The Senate’s “Contacting U.S. Senators” page lists every senator by state, with their website and Washington phone number. The House’s “Find Your Representative” tool matches your ZIP code to your congressional district and links to the member’s site.
Write to your own members. The Senate says plainly that many senators “will acknowledge, but not respond to, a message from another senator’s constituent”.
Find your senator’s or representative’s fax number
Neither the Senate nor the House lists fax numbers centrally. Each member’s website does, if the office takes faxes: look on the Contact or Offices page, and sometimes in the page header beside the Washington phone number. Many list a Washington fax and another for each state or district office.
Some offices don’t publish a fax number at all and ask you to use their web form instead. If you can’t find one, call the Capitol switchboard on (202) 224-3121; the operator will put you through to the office, and you can ask which fax number to use.
Numbers change when members do. A new Congress starts on 3 January, so after an election, check the member’s own site on the day you send.
Washington or the local office?
For a view on a bill or a vote, the Washington office is where the legislative staff work, so send it there. For help with a federal agency, such as Social Security, the VA or the IRS, ask which office handles casework; it’s often the one in your state or district. Expect it to need a signed privacy release before it contacts the agency for you: one House office’s FAQ says the release is required. Faxing the signed form saves the week or two that mail would take.
If the agency itself takes faxes, it can help to send your documents there as well: we cover the Social Security, VA and IRS fax numbers.
What to put on the page
- Your full name, home address with ZIP code, phone number and email at the top. The address is how the office knows you’re a constituent, and the Senate asks for a return postal address.
- The date, and a one-line subject: the issue, or the bill number. Congress.gov’s glossary explains the prefixes: H.R. for a House bill and S. for a Senate bill.
- One issue, in a few short paragraphs: what you want the member to do and why it matters to you.
- For a case with an agency: your reference number, a short timeline, and the signed privacy release.
- Your signature. Keep it to one page if you can, plus a cover sheet addressed to the office.
Our fax cover sheet generator makes the cover sheet. Put the member’s name and office on it, and your ZIP code.
Send the fax
You don’t need a fax machine. From a phone, Municorn Fax scans your signed letter or release form with the camera, sends it to the office’s number and keeps a confirmation page with the date and time it went through. The first single-page fax is free, which covers a one-page letter. EveryFax does the same from a computer or by email.
There’s also a free option for Congress specifically: FaxZero lets you send faxes to members free, from a list by state and district, and marks the offices that aren’t accepting faxes. It doesn’t show the numbers themselves. Our roundup of free fax services covers its limits.
Frequently Asked Questions
Can I fax a senator from another state?
You can, but don’t expect a reply. The Senate notes that many senators acknowledge but don’t respond to messages from another senator’s constituents.
What if the office doesn’t list a fax number?
Use its web form, or call the Capitol switchboard on (202) 224-3121 and ask the office for a fax number. Some offices simply don’t take faxes.
Is it free to fax Congress?
It can be. FaxZero sends faxes to members of Congress free from its own list. Through an app, the first single-page fax is free with Municorn Fax.
Should I send the same fax to both senators and my representative?
Yes, if the issue is in front of both chambers. Address each one to that member, with their name on the cover sheet, rather than one letter to all three.
Sources
- U.S. Senate, “Contacting U.S. Senators”: senators by state, web forms, the Capitol switchboard (202) 224-3121; no fax numbers listed. Checked 18 October 2026.
- U.S. Senate, “Contacting the Senate”: include a return postal address; many senators acknowledge but don’t respond to another senator’s constituents. Checked 18 October 2026.
- U.S. House of Representatives, “Find Your Representative”: ZIP code lookup; no central list of member contact details. Checked 18 October 2026.
- A House member’s constituent services FAQ (NC-5): postal security adds one to two weeks; a signed privacy release is required for agency help; Washington and district fax numbers. Checked 18 October 2026.
- A House member’s Washington office page (WA-1): a fax number in the page header; mail called the slowest method. Checked 18 October 2026.
- FaxZero, fax your representatives: free faxes to members, offices not accepting faxes marked; data updated 18 October 2026. Checked 18 October 2026.
- Congress.gov, Glossary of Legislative Terms: bill prefixes. Checked 18 October 2026.
- Constitution of the United States, 20th Amendment: terms end and the new Congress assembles at noon on 3 January. Checked 18 October 2026.
