If a customer returns an item and exchanges it for another, you do NOT edit the old sale in the computer. An exchange is also handled like a standard sale, except for the following:
When prompted for the stock number, type the item being returned. For the quantity, type -1 (negative 1). This lets the system know that you are adding the item back into inventory instead of taking it away.
Leave the price of the item as a positive amount, as you would for a normal sale. (The program will multiply the —1 qty times the price for the credit.)
Type the new item’s SKU number, price and quantity, as usual when selling an item.
The system will automatically calculate the difference between the returned item and the new item. If the result is that the customer owes you the difference, accept the payment as you would for a regular sale. If the you owe the customer a refund, record the refund as described in the previous section
Note that in an exchange, it does not matter whether you enter the returned item or the new item first.