I have a customer who is also a vendor. I have paid his bill minus what he owes us. How do I credit his receivable with the shortfall from my payment?
QB can't do it directly with one transaction because it cannot handle a transaction that impacts both AP and AR accounts.
Instead, this is done by creating a fake AP payment and a fake AR payment, which will cancel each other out when recorded against a bank account.
In turn, these transactions are sometimes posted to a "wash" bank account (a bank account on your chart of accounts that does not represent an actual account in the real world) or perhaps to a petty cash "bank" account - if you have an account set up for this purpose.
@Anonymoushas given you good info. I have a Bank Account set up that I call Internal Clearing. The entire purpose of it is to handle transactions like these that can't be accomplished in one step in Quickbooks. Of course the desired end is to always have that account at a $0.00 balance so it won't ever show up on your financial statements. If there's anything other than $0.00 in there, then you will know that something has gone wrong. Good luck!