Inventory Management
Negative inventory is when a product's recorded stock count drops below zero, usually because it sold after Shopify already thought there was none left.
Negative inventory just means the number on a variant has gone below zero. Not "we're out." Actually negative, like minus four units.
This isn't always a sign something's broken. If a store has overselling allowed on a product (Shopify calls this the "continue" inventory policy), it's expected behaviour. Customers can keep ordering after stock hits zero, and the count just keeps counting down.
It's a different story if overselling isn't supposed to be allowed on that product. Under Shopify's normal "deny" policy, stock shouldn't be able to go negative through regular sales at all. If it has, something else is going on, maybe a sync issue, maybe a fulfilment problem, and it's worth investigating rather than assuming it's fine.
Ghost Stock treats these two situations differently. Negative stock under an explicit overselling policy is flagged gently, as expected. Negative stock without one is flagged more seriously, because it genuinely shouldn't happen under normal conditions.