A confirmation proves the machine answered, and that is all

Fax runs a handshake, T.30, between the two machines. The sender offers a page, the receiver takes it, and after each page the receiver sends back a message that means “that one arrived.” Those acknowledgments are the entire factual content of a confirmation. Count them and you know how many pages the far end took.

The handshake also carries a remote station identifier — a short string the answering machine reports about itself, often a phone number or an office name. It is recorded on your transmission record when the machine sends one. Treat it as what it is: self-reported and unverified. A machine can be configured to say anything, and plenty are configured to say nothing.

What the protocol has no way of expressing: whether the paper ran out after the call, whether the pages went to the right department, whether anybody picked them up off the tray, or whether the organization considers your submission received.

A fax call that drops at page 22 of 30 is not reported as a failure. Carriers report it as a success, with a page count lower than the one they were given — which is accurate, and which taken at face value means a customer is charged for a document the recipient does not have, and receives a record whose own numbers quietly admit it.

Here, a short count is a failure. If the receiving system does not acknowledge every page we handed the carrier, the transmission is not confirmed, the authorization on your card is released rather than charged, and the attempt is retried. A confirmation from us therefore means every page, not most of them.

This is worth knowing wherever you send from, because it is a real difference between services and not one anybody advertises. If you have a confirmation page from any fax service, compare its page count to the number of pages you sent.

• —The destination number dialed, and the recipient name you entered if you entered one
• —Pages in the fax, and pages the receiving system acknowledged
• —Start and end timestamps for every attempt, not just the one that worked
• —The reason each unsuccessful attempt ended
• —The remote station identifier the answering machine reported, if any
• —The carrier's transaction ID, which is the reference a carrier can trace
• —SHA-256 hashes of each file as we received it and of the assembled fax pages

The hashes are the part that makes the record checkable rather than merely official-looking. The document itself is deleted; the hash is not. Hash your own copy later and, for a PDF, a matching value ties the file on your disk to this transmission, because a PDF reaches us unchanged. A photograph is shrunk on your device before it is uploaded, so its hash is of the shrunk file and will not match the original.

The receiving fax system answered and acknowledged the page transmission shown above. This does not confirm that a person reviewed the document, that the recipient organization routed or accepted it, or that any filing requirement or deadline was legally satisfied.

It is on the record itself, verbatim, rather than in terms of service nobody opens. A record that claimed more than the fax network told us would be worth less to you, not more — the first time it was tested against somebody who knew the protocol, everything else on it would become questionable too.

Send them the record. It is a dated PDF stating what we sent, to what number, when, and how many pages were acknowledged, and that is the strongest artifact a fax produces.

Whether it satisfies a given requirement is that organization’s rule and not something we can tell you. Many agencies that accept fax filings treat the transmission timestamp as the filing time; some require a confirmation to be retained; some do not accept fax for that submission at all. The office that asked for the document is the authority, and their instructions are where the answer is. We do not give legal or tax advice, and a service that told you your fax “counts” would be doing exactly that.

If a transmission did not complete, when a fax fails covers what the reasons mean and which are worth retrying.

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