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Fax a double-sided document by sending both sides of every sheet in order, front then back, and confirming the recipient received both sides, because a standard fax feeder only scans one side of each sheet. The safest method is to copy the backs onto separate pages first, then fax the full single-sided stack in order, with a cover sheet stating the total page count.
Most fax machines and scanners feed each sheet once and scan one side. If you load a double-sided stack into a single-sided feeder, the backs never get scanned, and the recipient receives only half the document without any warning that pages are missing. The confirmation page will still report a successful send, because from the machine point of view, every sheet it fed was sent. The missing backs are silent, which is why double-sided documents are a classic fax failure.
Some multifunction machines offer two-sided scanning, but that feature is not universal, and the receiving side cannot tell whether a page it received was a front or a back. Even with two-sided scanning, page order can confuse the recipient: if backs are interleaved differently than expected, the document reads out of order. The copy-first method avoids both problems by turning the document into a plain single-sided stack.
| Method | How it works | Risk |
|---|---|---|
| Copy backs first | Photocopy each back onto its own page, then fax the stack in order | Low, if the page order is checked |
| Two-sided scan, if available | Machine scans both sides in one pass | Order confusion, and not all machines offer it |
| Feed double-sided stack as-is | Feeder scans one side only | High: backs silently missing |
| Flip sheets by hand mid-send | Send fronts, then reload and send backs | Medium: order mix-ups and duplicate pages |
First, count the sheets and note how many have writing on the back. Photocopy each back onto a separate page, and arrange the stack as front, back, front, back, so the fax reads in the same order as the original document. Number the pages by hand in the corner if the document is long, so the recipient can spot a missing page at once. Remove blank backs from the count: a sheet with a blank back should not produce a blank fax page, since blank pages can look like transmission errors to the receiver.
Second, write a cover sheet stating the total page count including the copied backs, and noting that the document was double-sided in the original. That cover sheet is what lets the recipient check completeness: if they count fewer pages than the cover sheet states, they know to ask for the missing ones. Third, after sending, confirm with the recipient that they received the full count and that the backs are present and readable, not just that pages arrived.
Blank-page traps are the most common. A blank back copied as a blank page can make the recipient think the fax failed partway, and some machines skip blank pages entirely, which throws the page count off. Mark genuine blank pages as intentionally blank only if the document requires it, and otherwise leave them out. Another trap is show-through: writing on thin paper can bleed through to the other side and appear as ghost text on the faxed copy. If show-through appears, copy the pages onto thicker paper before faxing.
For LetterAgent faxing to US and Canadian numbers, prepare the document as a single-sided stack before sending: you ask your AI assistant, get a per-fax quote with the page count verified, approve the exact total, and pay once through Stripe. Fax is currently in testing, so it is described as available in testing and a fax is never promised to send on a particular day. Verify the page count on the quote matches your prepared stack, including the copied backs.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
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