Information you can expect to fill out includes the car's VIN, make, and model, the name and permanent address of each party involved, and the sales amount. The final hurdle you face is signing the vehicle purchase agreement; a confusing and convoluted document that we explain in detail here.How do I fill this out? Filling out the Motor Vehicle Purchase Agreement is straightforward. Customize the Template: Carefully fill in all the necessary information, ensuring accuracy and clarity. Here are six of the most important documents you'll be asked to sign when you're making a deal on a car. We'll also point out which section matters most. A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services. It is also used to calculate use tax on motor vehicles brought into Texas that were purchased from a private-party out of state. What are your life goals?