@ronhu You might have noticed that there are two options (Order ID and Payment Date) in the Acknowledged Supplier Payment window to view data. If you have acknowledged a payment order when the Payment Date view is used, the unacknowledgment also should be done in the same view. In you case, it looks like you have acknowledged the order with the payment date and now going to unacknowledge it via Order ID view. So, go back to the Payment Date view and unacknowledged the lines. The reason for this validation is there can be payment order lines with multiple payment dates within a single order. So, you might not required to acknowledge the whole order at once.