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The fax header line is the strip of text printed at the very top of every received fax page, identifying the sender: a name or station ID, the sending phone number, the date and time, and the page number. It is stamped on each page as the fax transmits, and in the US it is not optional: federal rules require it on every fax you send.
| What the header usually shows | Example | Why it matters |
|---|---|---|
| Sender ID (station ID) | ACME DENTAL | Lets the recipient know who sent it at a glance |
| Sending phone number | 1-555-555-0100 | Required by US law; the number to call back |
| Date and time | OCT-09 06:45 | Proves when the fax was transmitted |
| Page count | P.03/05 | Shows the recipient whether all pages arrived |
Junk faxes. The US Telephone Consumer Protection Act requires every fax to carry the date, time, sender identity, and the telephone number of the sending machine, printed along the top or bottom edge of the first page or every page. The rule exists so recipients of unsolicited faxes know who is bothering them and can complain or sue. Enforcement is complaint-driven, but the requirement is real, and every legitimate fax machine has a settings menu where you program your station ID and fax number so the header fills in automatically. A fax that arrives with a blank or fake header is a red flag: it is exactly what junk-fax operations use to dodge identification.
Look in the settings menu for "station ID," "sender ID," "TTI" (transmit terminal identification), or "header." You enter two things: your business or personal name, and the phone number of the fax line. The machine then prints that along the top edge of every page it sends. One detail people miss: the number in the header should be a voice number where you can actually be reached, not just the fax line itself, since the whole point is to give the recipient someone to call. If you recently changed numbers, update the header: an outdated number in the header confuses recipients and looks sloppy.
Online services generate the header automatically, using the fax number assigned to your account or the email address behind the send. A header that shows an email address or a number the recipient does not recognize is normal for online faxing, but it can confuse automated recipient systems that expect a conventional phone number. If you fax a government agency or a large institution regularly, check that their intake recognizes your online fax number: some systems match incoming faxes against an approved-sender list, and a number that was not registered in advance can be rejected or quarantined.
No, and they serve different purposes. The header is machine-generated metadata: who sent it, when, and how many pages. A cover sheet is a document you write: who the fax is for, what it contains, how many pages follow, and your contact details. A fax without a header looks anonymous and may violate the rules; a fax without a cover sheet is merely rude in a business context. Use both: the header proves the transmission, the cover sheet tells the recipient what to do with it. With LetterAgent, you send a fax by asking your AI assistant: per-fax quote with the page count verified, you approve the exact total, pay once through Stripe, and the fax is sent with a proper sender header. LetterAgent covers US and Canadian fax numbers only and cannot receive inbound faxes. Faxing is currently available in testing while activation is in progress, so treat it as available in testing rather than guaranteed.
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