Backorders allow your store to continue selling products after the quantity reaches zero, or is effectively out of stock. When a customer order is a backorder, the funds are authorized and captured immediately, the processing status of the order does not change, and the shipping remains on-hold until stock is available.
Notify for Quantity Below
The Notify for Quantity Below configuration option is configurable at the global, source, and product levels. When it is enabled, the system sends an email notification when the product quantity reaches a level at or below the configured value. For this example, a notification is triggered when the product has a quantity of 10 or less. When backorders are enabled, Notify for Quantity Below is determined by the Salable Quantity (Salable Quantity = Quantity - (Out-of-Stock Threshold)).
Products must be set to In Stock status when enabling backorders. You can set this through the Product page. For multi source merchants, you must have at least one source marked as In Stock. Access and set the status through the Product page and assigned Sources grid.
Understand backorder settings
We recommend configuring specific thresholds and settings to best support backorders. Please read related articles for more details.