Shopify inventory does not match the warehouse when more than one system is allowed to change the same number. A location, an app and a spreadsheet each think they are the source of truth.
Pick one source of truth. In Shopify, check which locations fulfil online orders, turn off overselling where you cannot backorder, and pause every extra inventory app except the one that syncs the warehouse.
Where the number drifts
- Online Store fulfils from a location you do not count
- A returns app and an ERP both write available quantity
- Bundles sell components that were not decremented
- A draft order or POS sale never synced back
Overselling also feeds payment reviews when you refund orders you cannot ship.
What we build when apps are not enough
ERP and warehouse connections are Shopify ERP integration work, then monthly maintenance so the sync keeps running after the other system updates. Do not start with a theme change. Stock is not a design problem.
Send which system should win and how often it must sync. Ask about an inventory integration.
