34 Tex. Admin. Code § 43.6
All documents relating to any appeal of a final administrative decision shall be filed with the deputy director at TRS, 1000 Red River Street, Austin, Texas 78701-2698. A document may be filed with TRS by hand-delivery, courier-receipted delivery, facsimile transmission, or regular, certified, or registered mail. A document is deemed filed when mailed if it is received by TRS within a timely manner under Texas Rule of Civil Procedure 5 and the sender provides adequate proof of the mailing date. If the deputy director has docketed an appeal and referred it for an adjudicative hearing, documents shall be filed with the administrative law judge and a copy provided to the TRS docket clerk during the time the matter is pending before the administrative law judge.
34 Tex. Admin. Code § 43.6