Many different forms of interference can occur between the sender and recipient of a fax during transmission. This can result in the fax documents to be transmitted being incomplete or illegible or not arriving at the recipient at all. Decisions based on this information may be inappropriate, which can result in significant losses or damage.

Delays that occur because problems have to be identified and documents need to be resent can lead to further complications. The transmitter or receiver usually has no way of influencing the transmission path and thus has to wait until the interference has been rectified by a third party. In many cases, the sender even believes that a faxed document has been properly transmitted to the desired addressee and the resulting problems are only detected some time later.

In addition, it cannot be ruled out that a fax document may have been transmitted to the wrong recipient machine due to a faulty connection in the public telecommunications network, for example. Wrong numbers may also be dialled on fax machines, or the direct dial keys may have been incorrectly programmed. If a fax server is used, fax numbers may also have been entered or stored incorrectly in the address book. As a result, confidential information may be sent to unauthorised persons.