Tex. Tax Code § 111.107
(a) Except as otherwise expressly provided, a person may request a refund or a credit or the comptroller may make a refund or issue a credit for the overpayment of a tax imposed by this title at any time before the expiration of the period during which the comptroller may assess a deficiency for the tax and not thereafter unless the refund or credit is requested:
Acts 1981, 67th Leg., p. 1508, ch. 389, Sec. 1, eff. Jan. 1, 1982.
Amended by Acts 1989, 71st Leg., ch. 232, Sec. 2, eff. Sept. 1, 1989;
Acts 1993, 73rd Leg., ch. 587, Sec. 8, eff. Sept. 1, 1993;
Acts 1997, 75th Leg., ch. 1040, Sec. 7, eff. Oct. 1, 1997;
Acts 1999, 76th Leg., ch. 1467, Sec. 2.14, eff. Oct. 1, 1999;
Acts 2003, 78th Leg., ch. 1310, Sec. 89, eff. June 20, 2003.
Acts 2009, 81st Leg., R.S., Ch. 1227 (S.B. 1495), Sec. 5, eff. September 1, 2009.