When a customer good is depleted, it will be identified for back order if there is not sufficient stock available to fulfill the item order. A pink X status icon will automatically be applied to the item to indicate that it is on back order. 

The Details tab of the item will also show the customer goods status as Back Ordered.

On the Customer Good view page, any back ordered items for the selected customer good will appear on the Back Orders table.

When the customer good is replenished, these back orders will automatically be fulfilled based on item order date. For more information on replenishment, see Customer Goods - Replenishment.