I have always been a fan of quoting the language of the statute involved in alleging most any violation of the criminal law. So, how about:
after having collected, as a dealer, motor vehicle sales tax as required by Chapter 152 of the Tax Code, did then and there intentionally or knowingly fail to pay said tax to the tax assessor-collector, and the value of the tax collected was $1500 or more but less than $20,000 ?
I would bet the Travis County District Attorney has a form as well.