Hi, as far as i can remember bank personnels know if the client is telling the truth or not. In case there is a complain like machine didn't dispense the cash, they have to make complaints right there and then and fill up a form. Then the Cashier or Cash Custodian or any authorized bank personnel who does the refill of cash on trays does the balancing of the same at the end of the day. There is a receipt that indicates the cash in and out. Amount on the balance should tally with the actual cash. They will know if there is excess cash.