You give a receipt when you exchange money. That's it. If they want to then make a copy or a thousand copies of the receipt you give them that's their perogative. But if you give multiple receipts, on papers with different serial numbers or on a statement that doesn't show the balance before and after the payment was received, then you're asking for trouble as it could be claimed that they gave you an extra payment. They have a receipt afterall.I do all my rental receipts via text message today. I text them a balance owed. When I receive payment I text the amount received and what the new balance is, ideally $0. But sometimes its easier to just overpay or underpay by a few dollars instead of getting coins and that's fine. I have a recorded date and time of the amount owed, recorded date and time of them acknowledging the debt, recorded date and time of me receiving payment. Very easy.