This article explains how to account for an early supplier payment discount in KashFlow.
To start, you should set up a purchase code called Early Payment Discount by going to Settings > Purchase Codes > Click Add Purchase Code at the bottom of the page.
Once this is done, navigate to Purchases > Create > Select the supplier > Add Line Item using the code you just created. Please add a minus in front of the line item total to reflect the discount you have received and leave it unpaid.
If you then go to the original receipt you wish to discount, you will notice an Apply Credit button within the Payments section at the bottom.
Simply click the button, tick the discount you have just created and press the Apply button. Now both receipts will be marked as paid.