(a) The comptroller shall employ auditors and other technical assistants to verify reports and investigate the affairs of producers and purchasers to determine whether the tax is properly reported and paid.(b) A producer who has failed to pay the proper amount of tax, a penalty, or interest due is liable for the reasonable expenses incurred by representatives of the comptroller in the investigation or the reasonable value of their services. The amount for which the producer is liable under this subsection is an additional penalty. Acts 1981, 67th Leg., p. 1732, ch. 389, Sec. 1, eff. Jan. 1, 1982.