A bill of sale is a document for a sale or, using legal terms, a transfer of ownership of property. Some states require a bill of sale for a horse and some do not, but it is always a great idea to create one for a personal record. Bill of sales for Horses include a description of the horse being sold, breeding information, veterinary exams, and information about the parties in the transaction and signatures of the parties. These documents can be notarized by a notary public, but few states make this a requirement.