The Texas bill of sale form verifies the elemental facts of the sale of personal property in exchange for a predetermined compensatory amount. County of Harris. §.Bill of Sale "; Texas. 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. This transaction is made in the County of. ,. The form consists of the significant vehicle, buyer, seller, and sale data, along with affirming signatures from both parties.