Texas Tax Code - TAX § 151.339. Preexisting Contracts and Bids

(1) the services are used for the performance of a written contract entered into prior to the date this chapter takes effect if the contract is not subject to change or modification by reason of the tax; or

(2) the services are used pursuant to an obligation of a bid or bids submitted prior to the date this chapter takes effect if the bid or bids may not be withdrawn, modified, or changed by reason of the tax imposed by this chapter; and

(3) if notice of a contract or bid on which an exemption is to be claimed is given by the taxpayer to the comptroller within 60 days from the date this chapter takes effect.