What is a fax number?

A fax number is a phone number that's answered by a fax machine or a fax service instead of a person. In the U.S., it looks just like a phone number, with a 3-digit area code followed by a 7-digit number.

What a fax number looks like

In the U.S. and Canada, a fax number has 10 digits, the same as a phone number. You might see the same number written in any of these ways.

• (206) 555-0142
• 206-555-0142
• +1 206 555 0142

The +1 at the start is the country code shared by the U.S., Canada and several Caribbean countries.

The numbers above are examples, not real fax lines.

Fax number vs. phone number

The two look the same, and the difference is what answers the call. A fax only goes through when a fax machine or fax service picks up, so if a person or voicemail answers, the fax fails.

Many offices have a phone number and a separate fax number. Use the exact fax number on the form or letter that asked for the fax.

For an IRS form, our guide to finding the right IRS fax number shows where each form's number is listed.

How to find someone's fax number

• Look at the form or letter that asked for the fax, which often says "Fax to" or "F:" next to the number.
• Check the office's website, on the contact page or at the bottom of the page.
• Check an email signature from the office, since offices often list a fax number there.
• Call the front desk and ask for the fax number, and for the name of the person the fax should go to.

Don't guess. A fax sent to the wrong number can end up with a stranger.

For a fax to Social Security, our guide on finding the right Social Security fax number shows where each office's number is printed.

When you need your own fax number

You don't need one to send a fax, only the fax number of the person or office you're sending to.

If you don't have a fax machine either, our guide shows how to fax without a fax machine.

You do need one to receive a fax, because the sender needs a number that a fax machine or fax service answers. Online fax services that offer fax numbers can give you one. Some FedEx Office locations can receive a fax for you to pick up, and The UPS Store lists receiving faxes as a service.

Our guide to where you can fax something near you lists what each store says about receiving faxes.

As of November 2026, on faxfair.com you can get a US fax number online for 7 days ($4.99), 30 days ($9.99) or 1 year ($59.99). We email each fax sent to it to you as a PDF attachment, or as a link to your inbox page if the fax is over 10 MB. The FaxFair iPhone app sells numbers at the same prices, and faxes sent to a number you buy in the app arrive in the app. Neither kind renews by itself.

Once you have the fax number, you can send the fax from this website. Upload your PDFs or photos and type the number, and a private status page follows the fax until it's delivered or fails. If your pages are on paper, the FaxFair iPhone app can scan them with the camera and send them.

Send a fax online

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