When you enter a customer payment for an invoice, the Receive Payments window has a “Discount Info” button. You can use this button to give the customer a discount if your payment terms include a discount for payment before the due date. Even if the customer has sent you a payment for the full amount of the invoice, you can apply a discount.
Note: To apply discounts to statement charges, go to the Accounts Receivable register for the customer and use a Discount item.
QuickBooks calculates a suggested discount amount based on your payment terms with the customer and the payment date.