The available quantity of a part refers to the amount within the warehouse which can be allocated to an order line if required.

This equates to the amount of stock on hand, discarding stock already allocated, the stock which has been reserved for use as a component in a firmed job, and other miscellaneous allocations such as a move out of the warehouse. The on-hand quantity is credited on receipt of purchase orders, jobs, or incoming stock moves from other warehouses.

An order line is considered 'out of stock' when the demand for stock on an order line is greater than the available quantity.