Hello there @TH-GFL, thanks for reaching out to the Community!
I am happy to look at some reasons why you may be seeing these discrepancies. Some possible reasons we may be seeing this:
Note: if you are using different units of measure, there is no workaround at this time. The item QuickReport is displaying the quantity from the transactions without converting it to the base unit. Intuit is aware of this issue and is working on a resolution. Here are some steps we can use to work around this limitation:
All pending invoices will be removed from the QuickReport, and the quantity on hand value will match the item’s quantity on hand on the items list. Let me know if you have questions on this, or if this does not work so we can explore other options. Take care!