There needs to be a preference that prevents the system from accepting a transaction that would produce a negative balance or credit. Not everyone wants to deal with credits.
It would be really great for this preference to be tied to the itemlost authorized value. We use a different value for Lost and Paid for and Damaged - any item that has these statuses that is turned in should not result in a automatic credit that would either reduce other outstanding fines or create a negative balance/credit.