County of Harris. §. It contains information about the buyer and the seller, a description of the vehicle being sold, and information about the transaction, such as price.Used trailer less than or equal to 4,000 lbs. How to fill out the Texas Vehicle Bill of Sale Form? The Houston Vehicle Bill of Sale is a form used for selling and conveying a vehicle or trailer to another party. All "Component Parts" listed on this form must be from the same vehicle and sold to an individual purchaser. Bill of Sale to a Motor Vehicle. MV-028. Each state has specific requirements for the registration and titling of a trailer. Find out what they are in Texas and when you need to use a bill of sale. Contact the county tax assessor's office or the Texas Department of Motor Vehicles (DMV) for the agency's name.