(a) Except as provided by Subsection (d), a seller who makes a sale subject to the sales tax imposed by this chapter shall add the amount of the tax to the sales price, and when the amount of the tax is added:
(1) it becomes a part of the sales price;
(2) it is a debt of the purchaser to the seller until paid; and
(3) if unpaid, it is recoverable at law in the same manner as the original sales price.
(b) The owner or former owner of tangible personal property, a factor of the owner or former owner, or an agent of the owner, former owner, or factor shall collect the sales tax and add the amount of the tax to the sales price of the tangible personal property if the person delivers the property to a consumer in this state or to another person for redelivery to a consumer in this state under a sale of the property that is not a sale for resale and that is made by a seller not engaged in business in this state.

(c) When several taxable items are sold together and at the same time, the sales tax is determined on the sum of the sales prices of the items sold exclusive of any item the sale of which is exempted by this chapter.
(d) For purposes of the printer’s tax collection duty, it is presumed that printed materials that are distributed by the United States Postal Service singly or in sets addressed to individual recipients, other than the purchaser, and that are either produced at a printer’s facility in this state or purchased in this state are for use in Texas and the printer must collect the tax imposed under this chapter. In order to overcome this presumption a purchaser of printed materials that are distributed by the United States Postal Service singly or in sets addressed to individual recipients, other than the purchaser, is required to issue an exemption certificate to the printer if the printed materials are for distribution to both in-state and out-of-state recipients. The certificate must contain the statement that the printed materials are for multistate use and that the purchaser agrees to pay to this state all taxes that are or may become due to the state on the taxable items purchased under the exemption certificate. In this subsection, “printed materials” is defined to be materials that are produced by web offset or rotogravure printing processes. A printer is relieved of the obligation of collecting the taxes imposed by this chapter on printed materials that are distributed by the United States Postal Service singly or in sets addressed to individual recipients, other than the purchaser, but is required to file a report as provided by § 151.407.