Data damage and file repair
When an inventory part shows fewer than zero units on hand, QuickBooks is carrying a negative quantity. It usually happens when a sale is recorded before the matching purchase, or when transactions are entered or dated out of order. The item list still works, but your inventory valuation, cost of goods sold, and balance sheet can drift out of agreement. These figures rarely correct themselves, so the underlying records need repairing rather than a simple adjustment on top.
Related service: Negative Inventory Repair