In the Ardex main program window select Finance at the bottom left, then select Credits and Transfers.
Enter an owner name, and a list of unpaid invoices for that owner will appear.
Enter a credit amount, date and reason for credit, then click in the Applied box next to any invoice that the credit relates to.
The income account selected for the original transaction will be used to offset the credit given to the owner (Cr Trade Debtors - Db Income Account)
The adjustment will also appear in finance >> adjustments should you need to remove this credit.