Possible payment discounts are calculated when an invoice is posted. The payment discount date (the latest date on which the customer can pay and receive a discount on the payment) is also calculated at this time.
Open the Sales Invoice window.
Press F3, and then press Enter to create a new invoice and give it a number.
In the Sell-to Customer No. field, select a customer with payment terms that allow payment discounts, and then click OK.
In the Posting Date and Document Date fields, enter a date.
On the first sales line, select an item, and then enter a quantity in the Quantity field.
Click Posting, Post to post the invoice.
Determining Base Amounts for Payment Discounts on Sales
Reverting VAT on Payment Discounts