A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services. By signing this contract, I choose to purchase the motor vehicle on credit according to the terms of this contract.Standard presumptive value (SPV) is used to calculate sales tax on private-party sales of all types of used motor vehicles purchased in Texas. Sale of Goods Agreement (Pro-Buyer, Short Form) (TX). (Pro-Buyer) (5-541-6567). Acceptable documentation includes a dealer's invoice or sales contract that itemizes the motor vehicle tax paid to the dealer. This legal document includes details about the vehicle, including its make, model, year, VIN, payment terms, and purchase price. Form of Master Loan Purchase Agreement from LendingClub Corp filed with the Securities and Exchange Commission. Form agreement for the sale of goods under Chapter 2 of the Texas Uniform Commercial Code (UCC), drafted in favor of the seller. Complete the Title: The seller must fill out the back of the title, including the odometer reading and the sale price.