Texas Finance Code - FIN § 345.064. Completion of Contract

(a) A person may not sign a retail installment contract that contains a blank space for an item that is an essential provision of the transaction.

(b) If delivery of the goods is not made at the time the contract is executed, the identifying numbers or marks of the goods or similar information and the due date of the first installment may be inserted by the retail seller in the seller's counterpart of the contract after the contract has been signed by the retail buyer.