Tex. Bus. & Com. Code § 304.101
In addition to complying with the technical and procedural standards established by federal statutes or regulations regarding telephone facsimile machines and transmissions, a person in this state who makes or causes to be made a facsimile solicitation shall include in the transmitted document or on a cover page to the document a statement, in at least 12-point type, containing:
(2) a toll-free or local exchange accessible telephone number of the person that:
Added by Acts 2007, 80th Leg., R.S., Ch. 885 (H.B. 2278), Sec. 2.01, eff. April 1, 2009.