I guess I see a receipt and/or a bill of sale for any purchase as just means to cover everybody's hind ends. Everyday example: When I buy gas and since i always pay at the pump, I will almost always get a receipt---just in case there's a screw up and the station mistakingly accuses me of not paying. If I buy something of considerable value from you, all I want is a simple piece of paper that acknowledges it was a mutually agreeable transaction and both parties agree it was satsfactorily completed. I don't want any more information transferred than required to adequately identify the parties involved.