Though standard form bill of sales are available online and from your local county tax collector's office, it's also perfectly acceptable to write your own. County of Harris. §.The Texas bill of sale form verifies the elemental facts of the sale of personal property in exchange for a predetermined compensatory amount. Sign the buyer's application for title: When selling a car in Texas, you'll need to sign the Buyer's Application for Title, which is Form 130U. Sample Motor Vehicle Bill of Sale.