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There is no single legal cap on fax pages, but three practical limits apply: the receiving machine's memory and paper, the online service's per-fax cap, and line noise that makes very long faxes fail mid-send. For long documents, split them into batches of 20 to 30 pages and keep the confirmation for each batch.
Two things: memory and paper. A traditional machine scans each page into memory before dialing, so a very long job can fill the machine's memory before it finishes scanning. On the receiving end, the machine prints as pages arrive: if it runs out of paper or toner halfway through, the rest of the fax is lost and you resend the whole thing. Office machines also tie up the phone line for the entire call, so a 100-page fax can block incoming calls for a long stretch.
Most do, though the caps are usually generous. Per-fax limits exist so one user's giant job doesn't clog the provider's sending queue for everyone else. The cover sheet counts toward the total in most services, so a nominal 10-page limit really means nine content pages plus the cover. When you hit a cap, the fix is the same as with machines: split the document into batches and send them as separate faxes.
A fax is a long phone call, and long phone calls are fragile. Line noise or a brief drop interrupts the session, and the fax protocol's error correction can only retransmit so much before the call times out. The failure usually lands near the end: the machine scans all 60 pages, dials, sends most of them, and drops. Some machines let you resend from the failed page, but many older ones start over at page one.
Error correction mode (ECM) is the quiet culprit behind slow long faxes. It retransmits garbled blocks so the received pages stay legible, which is exactly what you want, but on a noisy line those retransmissions stack up and a long fax slows to a crawl before it finally times out.
| Sending method | What sets the page limit | What happens at the limit |
|---|---|---|
| Physical machine | Memory, paper, and toner on both ends | Job fails partway; you resend the whole thing |
| Online fax service | Per-fax cap in the product | Send is rejected or queued; split into batches |
| Fax over VoIP lines | Call stability over a long session | Dropouts cause timeouts; retry in smaller batches |
If you ask your AI assistant to fax a long document through LetterAgent, the assistant verifies the page count before quoting, so you see the full size of the job up front. Per-fax quotes cover the whole batch you approve: nothing goes out without your sign-off. Fax is currently in testing and handles US and Canadian numbers only.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com