Just-in-Time is a method of manufacturing products which aims to minimise production time, production costs, and the amount of stock held in the factory. Raw materials and supplies arrive at the factory as they are required, and consequently there is very little stock sitting idle at any time. Each stage of the production process finishes just before the next stage is due to commence and therefore the lead-time is significantly reduced. With a just-in-time production system, the level of production is related to the demand for the output (the number of orders) rather than simply producing finished goods and waiting for orders. This means that raw materials and stock only need to be ordered from suppliers as required.

The just-in-time (JIT) inventory system minimises inventory and increases efficiency. JIT production systems cut inventory costs because manufacturers receive materials and parts as needed for production and do not have to pay storage costs. Manufacturers are also not left with unwanted inventory if an order is cancelled.

One example of a JIT inventory system is a car manufacturer that operates with low inventory levels but heavily relies on its supply chain to deliver the parts it requires to build cars on an as-needed basis. Consequently, the manufacturer orders the parts required to assemble the vehicles only after an order is received. For JIT manufacturing to succeed, companies must have steady production, high-quality workmanship, glitch-free plant machinery, and reliable suppliers.