47 CFR Section 68.318(d):
Telephone facsimile machines; Identification of the sender of the message. It shall be unlawful for any person within the United States to use a computer or other electronic device to send any message via a telephone facsimile machine unless such person clearly marks, in a margin at the top or bottom of each transmitted page of the message or on the first page of the transmission, the date and time it is sent and an identification of the business, other entity, or individual sending the message and the telephone number of the sending machine or of such business, other entity, or individual. If a facsimile broadcaster demonstrates a high degree of involvement in the sender’s facsimile messages, such as supplying the numbers to which a message is sent, that broadcaster’s name, under which it is registered to conduct business with the State Corporation Commission (or comparable regulatory authority), must be identified on the facsimile, along with the sender’s name. Telephone facsimile machines manufactured on and after December 20, 1992, must clearly mark such identifying information on each transmitted page.