(a) The receipts from the sale, use, or rental of and the storage, use, or consumption of taxable items in this state are exempt from the tax imposed by a county under this chapter if the items are used:
(1) for the performance of a written contract entered into before the date the tax takes effect in the county, if the contract is not subject to change or modification by reason of the tax; or
(2) pursuant to an obligation of a bid or bids submitted before the date the tax takes effect in the county, if the bid or bids may not be withdrawn, modified, or changed by reason of the tax.
(b) The exemptions provided by this section have no effect after three years from the date the tax takes effect in the county.
Official text of the Texas Tax Code as published by the Texas Legislative Council.