16 Tex. Admin. Code § 7.240
If the Hearings Division receives a letter or other communication from an affected person concerning a statement of intent filed pursuant to Texas Utilities Code, § RSA 104.102, the Hearings Division shall, within a reasonable time thereafter, forward to such affected person a form for filing a complaint and statement of intent to participate. The affected person shall complete the complaint and statement of intent to participate form and shall include the complainant's name, address, the utility and the rate increase that is the subject of the complaint, how the affected person will be impacted by the proposed rate increase, and a statement that the complainant or an authorized representative shall appear and participate through the presentation of evidence and arguments if a hearing is held to consider the rate increase. The affected person shall properly complete and return the complaint and statement of intent to participate form to the Hearings Division within 14 days after the mailing by the Hearings Division , or the Commission shall not consider it to be a properly filed complaint pursuant to Texas Utilities Code, § RSA 104.105. If the initial complaint is received before the deadline in Texas Utilities Code, § RSA 104.105, and the complaint and statement of intent to participate form is received after that date but in a timely manner pursuant to this rule, the form shall be deemed to be filed as of the date of the filing of the original complaint.
16 Tex. Admin. Code § 7.240