Tex. Nat. Res. Code § 161.509
(b) In addition to charging for late payments under Subsection (a), the board may set and impose a default rate of interest on:
Added by Acts 2001, 77th Leg., ch. 333, Sec. 2, eff. May 21, 2001.
Amended by Acts 2003, 78th Leg., ch. 674, Sec. 20, eff. Sept. 1, 2003.