Inputs, outputs and the cost of both
A factory's stock question is really a costing question. Quantities are tracked per warehouse with reorder points so a line does not stop for a component, adjustments carry documentation and an approval rather than being typed over, and cost of goods sold is calculated by FIFO, LIFO or weighted average as purchases and sales post — so margin on a job is a figure rather than a year-end estimate. Dispatch to a subcontractor for job work leaves under a challan, which is what keeps stock off the premises accounted for.
See how manufacturing runs it