Currently, if you manually update inventory using the CSV template and a quantity is negative (because it is oversold and on backorder), InkSoft replaces the inventory quantity for that SKU with a null value. This allows customers to continue purchasing as if the SKU has unlimited stock. At the very least, CSVs containing negative quantities should be rejected. Ideally the system would support negative inventory quantities so if we choose to allow backorders, customers could be notified.