Common causes
Unrecorded warehouse adjustments, delayed synchronization, returns waiting for inspection, transfers in transit and reservations can create different stock numbers.
Available-to-sell is not always physical stock
Physical units can still be reserved, damaged, returned or allocated.
Why multiple warehouses make it worse
More locations create more transfers, allocations and exceptions.
The operational fix
Connect storefront demand, warehouse stock, reservations, transfers, returns and purchasing in one inventory model.
Separate physical, reserved and available stock
One number cannot explain every inventory state. Teams should distinguish what physically exists, what is reserved for open orders and what is genuinely available to sell.
Create a stock movement audit trail
Every receipt, sale, transfer, return and adjustment should leave a trace. When stock differs, the team should be able to explain the movement history instead of manually reconstructing it.
Every event should remain connected to the product, contact or transaction that created it. That is what lets ERP explain a number instead of only displaying it.