In a taxing entity, there is imposed an excise tax on the use, storage, and other consumption within the entity area of taxable items purchased, leased, or rented from a retailer during the period that the sales tax is effective within the entity area. The rate of the excise tax is the same rate as the rate of the sales tax imposed by the taxing entity and is applied to the sales price of the taxable item.
Tex. Tax Code § 322.102