To run a business efficiently, merchants nowadays need to utilize technology such as websites, POS system, inventory, or an ERP system. However, no system is perfect, and there’s no guarantee that everything will run smoothly at all times.
In particular, in inventory systems that record a lot of transactions every day, the differences between theories and real quantity can happen in any period.
Human error or system issues are where the differences can come from. For example, your staff is unfamiliar with the system, so they record the wrong quantity when receiving items from the supplier.
Your system upgrade can also result in conflicts and data differences.