A completed Application for Texas Title and or Registration (Form 130-U); Applicable fees. The form consists of the significant vehicle, buyer, seller, and sale data, along with affirming signatures from both parties.A Texas Trailer Bill of Sale is a legal document used when transferring ownership of a trailer. A bill of sale benefits both the seller of a vehicle and the buyer. I Drive Safely will help you understand the importance of a Texas bill of sale. For used trailers, less than 4,000 pounds a bill of sale, and a copy of the registration are required. Any trailers that exceed a gross weight of over 7,500.