Gearbox uses Purchase Orders to order and receive Parts into Stock. If you do not wish to use the Purchase Order component of Gearbox, the only way to add Stock is through Stock adjustments.
Creating a Purchase Order with Parts (Purchase Order Items) will add to the On Order for the Part.
There are 2 methods to receive the Parts into Stock (Gearbox will move the Parts from On Order to Total Stock)
The first method is to click on each row in the Purchase Order and receive each part in the list:
However, this can be quite time consuming for a large list, so alternatively, you can check the box “All items on this purchase order have been received”
When save or save and continue is clicked, Gearbox will receive all parts on the Purchase order into Stock, indicated by the green tick: