Normally, when posting an invoice, a customer ledger entry is created resulting in a customer balance. However, when the invoice is a factoring invoice, the customer balance is automatically reversed with a payment transaction to the customer which moves the balance to a factoring account, either in the G/L or bank transaction (depending on setup).
Planned changes are to keep the customer balance on the customer, until final payment is made by the customer to the bank. When these changes are ready, we need more text explaining the new functionality.