(a) A sale of a taxable item by a person for delivery in this state is presumed to be a sale for storage, use, or consumption in this state unless a resale or exemption certificate is accepted by the seller.
(b) A sale is exempt if the seller receives in good faith from a purchaser, who is in the business of selling, leasing, or renting taxable items, a resale certificate stating that the property is acquired for the purpose of selling, leasing, or renting it in the regular course of business or for the purpose of transferring it as an integral part of a taxable service performed in the regular course of business.

(c) A sale is exempt if the seller receives in good faith from a purchaser an exemption certificate stating qualifications for an exemption provided in Subchapter H of this chapter.
(d) Properly executed resale or exemption certificates should be in possession of the seller at the time the nontaxable transaction occurs. If the seller is not in possession of these certificates within 90 days from the date written notice requiring possession of them is given to the seller by the comptroller or a later date agreed to by the comptroller and the seller, deductions claimed by the seller that require delivery of the certificates shall be disallowed. A deduction may not be granted on the basis of certificates obtained after the 90-day period or, if applicable, the date agreed to by the comptroller and the seller.
(e) Before allowing a deduction, the comptroller may verify the reason or basis for exemption claimed in a resale or exemption certificate acquired by the seller during the period provided by Subsection (d).