It looks like this is a duplicate post, MattMcG.   

My colleague Giovann  already shared his answer to your concern in QuickBooks Desktop. You can check his response through this link below. 

https://quickbooks.intuit.com/learn-support/en-us/reports-and-accounting/re-low-stock-alerts/01/1040.... 

You might want to learn more about inventory adjustment. This article will provide the information you need: Adjust your inventory quantity or value in QuickBooks Desktop. 

The QuickBooks Community team is always here to help if you have any other concerns or follow-up questions. Have a good one and stay safe!