40 Tex. Admin. Code §§ 819.191–819.201 § 819.200

(a) A motion for rehearing is required to exhaust all administrative remedies. A motion for rehearing must be filed not later than the 25th calendar day after the date the Commission decision is signed, unless the time for filing the motion has been modified by agreement between the parties and approved by the Commission. Any reply to a motion for rehearing shall be filed with the Commission not later than the 40th calendar day after the date the Commission decision is signed. A party filing a motion for rehearing or a reply to a motion for rehearing shall serve a copy on each party within the filing deadline using the notification methods set forth in §819.199(c). (b) The Commission may, by written order, extend the time for filing motions and replies and for taking Commission action. No extension may extend the period for Commission action beyond 100 days after the date the decision is signed. In the event of an extension, a motion for rehearing is denied on the date fixed by the written order or, in the absence of a fixed date, 100 days from the date the decision is signed. (c) If a party files a motion for rehearing, the Commission may: (1) grant such motion and remand for rehearing; (2) deny such motion, either expressly or by operation of law; or (3) render a decision and issue an order that no rehearing shall be necessary because imminent peril to the public health, safety, or welfare requires immediate effect be given to the final order. (d) If the Commission does not act on the motion for rehearing within 55 calendar days after the date the decision was signed, the motion is denied by operation of law and the decision is final. (e) A motion for rehearing must identify with particularity findings of fact or conclusions of law that are the subject of the complaint and any evidentiary or legal ruling claimed to be erroneous. The motion must also state the legal and factual basis for the claimed error.