The Suspected Inventory Problems by Warehouse Report is accessed through the Reports Window, Inventory folder and is used to display all Inventory Stock Items that have a potential difference issue.
For example: Stock Item MIRROR1 below has an On-Hand quantity of -1 (negative 1). Generally you would expect Invenotyr to be no lower than 0 On-Hand.
Further attention needs to be paid to these items. Most likely you will need to add Inventory Stock Adjustments to make the Items correct.
