You can include payables for which payment has already been created in set-off. Following posting their status changes from Z - To Pay to K - Set-off. Hence it is prevented that payables would be settled twice, that is, for the first time by setting-off and second time by payment order.
Example:
Create a payment order in total amount of the invoice for the invoice received 08-100-000025:

The moment the payment order is created its status is Z- To Pay. This means that it can be found in the Transactions module listed in the In Preparation panel:

The payable is included in set-off, but not entirely, that is, only partially in the amount of €219.61:

Clicking Close/post opens the Overview of Payment Order Changes window. Here you can observe that there was payment order 08-LI00-000032 created for document 08-1000-000037:

The payment order assigned To Pay status is split into two payment orders. On the one hand the one of them containing set-off amount is assigned the K - Set-off status. The other one with the Z - To Pay status is at the same time reduced for that amount.
Both payment orders appear in the document in the Payment Orders panel with Set-off and To Pay statuses respectively:

If you do not approve set-off then the status of the payment order changes to Z - To Pay. With this the payable is once again outstanding. Clicking the Reject button returns the following message:

Once more the entire amount of document 08-1000-000037 is displayed in the Payment Orders panel. The document is assigned the Z - To Pay status:
