It can happen to create vendor bills and customer invoices for the same contact (partner).

In the accounting app, it generates a receivable and a payable for the same contact. These accounts are set on the contact form (see below).

As a use case, I created a customer invoice and a vendor bill for this contact. Please see below the partner ledger linked to these entries :

Sometimes, we need to keep only a receivable/payable balance for the same partner so we need to aggregate the amount that he owes to us with the amount that we owe to him.

There is no magic trick to transfer a receivable amount to a payable amount (and the opposite). The only way to transfer an amount will be to create a journal entry (miscellaneous) with the both receivable and payable accounts linked to the same partner. There is no compensation so, basically you need to transfer the debt that the partner owes to the asset that you owe. 

To create this entry, we can reconcile all the receivable/payable journal items in the partner ledger. Please see in video : https://watch.screencastify.com/v/yeYaGIWkOdZ1cjHBHTcu