DenialFax · Q&A

What proof of delivery do I actually need for a fax appeal?

By Aman, Founder, Apellica. Last reviewed 2026-05-22.

Proof of delivery is the difference between an appeal that the carrier must respond to and an appeal the carrier can ignore. Without delivery proof, the carrier can claim it never received the document, and a member without a receipt has no recourse. With delivery proof, the carrier is on the regulatory clock from the timestamp on the receipt.

The minimum acceptable receipt for a fax appeal has four data points: (1) destination fax number (must match the carrier's published appeals number); (2) date and time of transmission completion; (3) total pages transmitted; (4) result code, which must read 'OK' or 'Success' (not 'Busy', 'No Answer', or 'Comm Error'). Receipts missing any of these four data points are not proof of delivery. They are proof of an attempt.

Home fax machines vary widely in what they print. Some print every send confirmation; some need to be configured to do so; some print only on errors. The safe move is to skip home machines entirely and use an online fax service. eFax, RingCentral Fax, SRFax, and Telnyx Fax (among others) all email a PDF transmission receipt automatically within seconds of send. The PDF is the receipt; save it.

Certified mail Return Receipt (USPS PS Form 3811) is the gold-standard delivery proof in US courts. It is admissible without further authentication under Federal Rule of Evidence 902. The signed green card (or its electronic equivalent) shows that an identified individual at the carrier's address physically received the envelope on a specific date. This is the proof that holds up in ERISA litigation if your case ever escalates.

Portal submissions create a case number, but they do not always produce a downloadable receipt. Take a screenshot of the confirmation page the moment it appears. Save it as a PDF with the date in the filename. The carrier portal will often log the submission internally, but you should not rely on the carrier to preserve evidence in your favor.

Storage. Keep all three (fax receipt, USPS Return Receipt, portal screenshot) for at least 4 years, ideally 6. The ERISA statute of limitations for filing suit is typically 3 to 6 years depending on the contractual clause, and the appeal documentation is the foundation of any future case. Store the PDFs in two places (cloud + local), named consistently, so you can produce them on demand.