Clearly print or type all information, except signatures. A New York Trailer Bill of Sale helps streamline the registration process and proves the transfer of ownership if a dispute arises.The proof of sale for a vehicle from a dealer is the Retail Certificate of Sale (MV-50) ("Dealer's Bill of Sale"). â–¡ Taxes are not included in the purchase price. 5. Use this free form for private transactions. It comes in a printable PDF format, and you can quickly fill it out using your completer. New York requires that you complete a bill of sale whenever you buy or sell a car privately. Use our NY bill of sale forms to prove the transfer of ownership of property from seller to buyer in the state of New York. A New York motor vehicle bill of sale provides proof that a motor vehicle has been legally sold and acquired in the State of New York. Out New York Notice of Lien (Form MV900) if the vehicle was financed.