Texas: 34 TAC §§ 3.161, 3.322

34 TAC § 3.161. Definitions, Exemptions, and Exemption Certificate. 
(b) Exemptions. This subsection deals with exemptions from the state hotel occupancy tax. For information on city and county hotel taxes, contact the affected city or county.
  (4) Diplomatic personnel of a foreign government who present an appropriate Tax Exemption Card issued by the United States Department of State are exempt from the tax.
  (5) If an exemption applies, then the organization or individual claiming exemption must present an exemption certificate to the hotel.

34 TAC § 3.322. Exempt Organizations.
(j) Diplomatic tax exemptions.
  (1) Sales tax exemptions provided to foreign diplomatic and consular personnel in the United States are governed by international and federal law as administered by the United States Department of State's Office of Foreign Missions.
  (2) Types of exemption cards.
     (A) Mission tax exemption cards. Mission tax exemption cards can only be used for official purchases by a foreign consulate or embassy. All purchases must be made in the name of the mission and paid for by a mission check or credit card, not by cash or personal check. The person whose name and photo appear on the card is responsible for ensuring the accuracy of the exemption, but does not need to be present when purchases are made in the name of the mission.
     (B) Personal tax exemption cards. Only the person whose photo appears on the front side of the card is permitted to use it to purchase the exempted items that are identified on the card. Personal tax exemption cards are not transferable and may not be used by others.
  (3) Procedures for retailers.
     (A) Diplomatic tax exemption cards must be presented to the seller at the time of sale for the exemption to apply. If the exemption is not claimed at the time of sale, the comptroller will not refund tax paid on an item which qualifies for a diplomatic tax exemption. The card must be signed.
     (B) To document the sale of an item subject to a diplomatic tax exemption, a retailer should retain a copy of the sales invoice or contract that bears the identification number appearing on the diplomatic tax exemption card or should make a photocopy of the front and back of the card.
     (C) Certain diplomatic exemption cards are limited to what and how much may be purchased tax free or may require a minimum purchase before the exemption can be claimed. This information is contained on the diplomatic exemption card itself. Retailers who make sales to persons with cards that require purchases to exceed a certain dollar limit should include only those taxable items that are purchased in the same transaction to determine if the appropriate level has been reached. Purchases made in separate transactions may not be added together to reach minimum exemption levels. Neither type of card identified in paragraph (2) of this subsection can be used to obtain the tax free sale of utilities.