Just-in-Time (JIT)
Just-in-Time (JIT) is a manufacturing and procurement principle in which materials, parts and assemblies are supplied only when they are actually needed in the production process – in the right quantity, at the right time, in the right place. The goal is to minimize inventory and tied-up capital by pulling material flow from actual demand instead of producing to stock.
Just-in-Time (JIT) is an organizing principle for production and procurement in which materials, parts and assemblies are delivered and made available exactly when they are needed for the next work step – not earlier and not to stock. Material flow follows actual consumption: each station only requests replenishment once it processes the material. This dramatically reduces inventory, storage space and tied-up capital, while lead times and buffers between production stages are kept as small as possible.
The concept emerged in the 1970s within the Toyota Production System and is today a core building block of lean production. JIT is not a single tool but an interplay of pull control, level production, short setup times, high process quality and tightly timed logistics. It requires stable, reliable processes – because where there is barely any buffer, every disruption, every quality defect and every late supplier immediately affects the entire chain.
At a glance
- Pull principle: material is pulled by demand, not produced to stock
- Goal: minimal inventory, short lead times, low tied-up capital
- Originated in the Toyota Production System / lean production
- Requires stable processes, short setup times and reliable suppliers
- Downside: high vulnerability to supply failures and demand spikes
How Just-in-Time (JIT) works
The core of JIT is the pull principle: unlike classic push control, which produces to stock based on sales forecasts, under JIT it is actual consumption that triggers replenishment. A production station withdraws material, and only this withdrawal signals to the upstream point – an internal earlier stage or an external supplier – that exactly this quantity should be reproduced or delivered. This creates a self-regulating chain in which inventory only exists in the amount consumed between two replenishment cycles.
For this principle to hold, several conditions must come together. Production is leveled (heijunka) so that demand stays even and predictable. Short setup times (SMED) make small batch sizes economical, so production can happen frequently in small quantities. High, stable process quality prevents defective parts from blocking the lean chain. And logistics must be tightly timed and reliable – often with several deliveries per day instead of one large weekly delivery.
Kanban as a control tool
In practice, pull control is frequently implemented via Kanban. A Kanban card (or an electronic signal) accompanies a container of parts; once it is empty, the card travels back and becomes a replenishment order for exactly this quantity. The number of circulating cards caps the maximum inventory in the system. Kanban is thus the operational implementation of the JIT idea at the shop-floor and procurement level, ensuring that – without central planning – only as much is in circulation as needed.
Benefits and relevance of JIT
The main economic benefit of JIT lies in drastically reduced tied-up capital. Inventory is money that is not working; it also causes storage, handling and interest costs and carries the risk of shrinkage, spoilage and obsolescence. Procuring material only at the point of consumption noticeably lowers these costs and improves metrics such as inventory turnover and return on capital. Less inventory also means less storage space – a real cost factor, especially at expensive production sites.
Beyond pure inventory reduction, JIT forces a company toward better processes. Because buffers disappear, weak points become immediately visible: unreliable suppliers, unstable machines, quality problems. JIT thus acts as a catalyst for continuous improvement, because problems are no longer masked by inventory. Shorter lead times also increase responsiveness to customer needs and shorten the time between order and delivery.
Limits and risks of Just-in-Time
The flip side of the lean chain is its vulnerability to disruption. Where barely any safety stock exists, every interruption – a supplier failure, a transport strike, a natural disaster – quickly leads to a production standstill, because no buffer bridges the gap. The supply chain crises of the early 2020s made this vulnerability clear and triggered a reassessment: many companies today combine JIT with targeted safety stock for critical parts or adopt a "just-in-case" approach for hard-to-replace components.
JIT is also not suitable for every situation. With strongly fluctuating or unpredictable demand, long replenishment times, distant single-source suppliers or parts with a high failure risk, the missing buffer can be more expensive than the tied-up capital. Frequent small deliveries also tend to shift inventory and transport effort into the supply chain – to the supplier or onto the road – which is not always sensible ecologically or logistically. JIT is therefore a deliberate trade-off between low inventory and supply security, not a universally correct answer.
Distinction: JIT vs. Just-in-Sequence and MRP
Just-in-Sequence (JIS) is a sharpened variant of JIT: parts are delivered not only at the right time and quantity but additionally in the exact assembly sequence – typical in automotive assembly, where seats or cockpits arrive in the sequence of the vehicles on the line. JIT describes the pull principle, while MRP (Material Requirements Planning) is a forecast-driven push method that calculates demand in advance from bills of material and sales plans. In practice the two are often combined: MRP plans the rough framework and capacities, while Kanban and JIT control the fine material flow at the execution level.
Just-in-Time (JIT) in the ERP system
An ERP system provides the informational basis for JIT. In planning and material requirements planning, it manages the consumption data, replenishment times and reorder points from which replenishment demand is derived. Through order proposals, framework agreements and delivery schedules, the ERP controls the fine-grained delivery: instead of individual orders, it calls off exactly the quantities needed in the short term against a framework agreement. Electronic Kanban signals, barcode confirmations from production and interfaces (EDI/API) to suppliers close the control loop, so that a material withdrawal automatically triggers the next call-off.
For JIT to work in the ERP, master and transaction data must be correct: up-to-date replenishment times, reliable real-time inventory management and clean integration with suppliers and warehouses. Incorrect inventory or outdated planning parameters immediately lead to shortages when buffers are low. Systems with integrated production planning (PPS) connect order control, capacity planning and procurement in a continuous data flow, so that demand, call-off and delivery stay tightly aligned.
Example
Example: Mid-sized machine builder
A mid-sized machine builder assembles equipment in small series and sources standard assemblies such as motors and controllers from a few fixed suppliers. In the past, the company stocked these parts in large quantities – expensive, space-consuming and with the risk that entire inventories became unusable when designs changed. With a JIT approach, it switches to framework agreements with daily delivery call-offs: based on the released assembly orders, the ERP reports demand, calls off the parts from the supplier two days before installation and schedules delivery to match the assembly start.
The inventory of expensive assemblies drops by more than half, storage space is freed up, and capital is no longer tied up on shelves. At the same time, the company learns the downside: when a motor supplier fails at short notice, an assembly line stands still because no buffer exists. The answer is not a retreat from JIT but a differentiated strategy – for non-critical standard parts it stays with call-off without inventory, while for hard-to-replace key components the company introduces a targeted safety stock.
Frequently asked questions
Matching ERP systems
Related services
Questions about Just-in-Time (JIT) in your ERP project?
We advise vendor-neutrally – and implement it ourselves on request.