If a customer returns an item and exchanges it for another, you do not edit the old sale in the computer. Instead, follow the same procedure as in the Customer Returns instructions above. The only difference is that after you type in the SKU number of the item that the customer is returning (with a negative quantity), on the next line type the SKU number of the item the customer are taking with her (with a positive quantity). If the item the customer is purchasing is more expensive than the item they are returning you can receive a payment for the balance as with any sale. If the item they are purchasing is less expensive than the item they are purchasing, the sale will have an overall negative total and you can process the refund as described above in the Customer Returns instructions.