If a taxable item is exempted from the taxes imposed by this chapter, the sale, storage, use or other consumption of the item is not subject to the sales tax imposed by Section 151.051 of this code or the use tax imposed by Section 151.101 of this code if the item meets the qualifications for exemption as provided in this subchapter; and when an item is exempted from the taxes imposed by this chapter the receipts from its sale are excluded from the computation of the taxes.
Tex. Tax Code § 151.301