Find out what documents you will need to provide proof of sale and ownership if you are buying, selling, or gifting a vehicle. In a private sale, have the seller make out a bill of sale in addition to the ownership and sales tax documents.Next Section. Continue. If Buyer extends, Seller may want to: (1) have Buyer bear the risk of changes in circumstances (e.g. I'm gonna break down all the terms and conditions so you can understand what it means and we're gonna fill that out so you can have a real-life example of it. A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services. The property and improvements which the Seller is agreeing to sell and which the Purchaser is agreeing to purchase is known as. New York requires that you complete a bill of sale whenever you buy or sell a car privately. General Bill of Sale – This form is usually utilized as proof between two private parties that a legal sale and purchase of personal items has been transacted. In a usual real estate transaction, the buyer and sellers' agents or attorneys would be the ones involved in creating the legal contracts.