Consignment Stock vs Vendor Managed Inventory for Spare Parts

Consignment stock and vendor managed inventory (VMI) are two supplier-stocking models where a supplier holds spare parts on or near your site, but they differ fundamentally in who owns the inventory and when you pay for it.

Under consignment, the supplier retains ownership until you consume a part, so cash leaves your account only at the point of use. Under VMI, the supplier decides what to replenish and when, yet ownership and payment usually transfer on delivery.

For maintenance teams juggling thousands of low-turn spares, choosing correctly changes your working capital, your stockout risk, and who carries the cost of obsolescence.

The core distinction: ownership and payment timing

The words are often used interchangeably on the shop floor, but the contract mechanics are different. Consignment is primarily a financial and ownership arrangement. VMI is primarily a replenishment and decision-rights arrangement. You can, in fact, run VMI on top of consigned stock, which is where most of the confusion comes from.

• Consignment stock: Parts physically sit in your storeroom, but the supplier owns them until a technician issues one to a work order. Title and invoice trigger at consumption. Unused stock can typically be returned or reallocated by the supplier.
• Vendor managed inventory: The supplier monitors your usage and stock levels and takes responsibility for replenishing them against agreed min and max targets. Ownership normally passes when the goods arrive at your dock, and you pay on standard terms whether or not the part is ever used.

Think of consignment as answering "whose money is tied up in this shelf?" and VMI as answering "whose job is it to keep this shelf full?" The two questions are independent, which is why a clean contract states both explicitly.

Cash flow and working capital impact

For a maintenance store carrying slow-moving critical spares, the cash-flow gap between these models is the headline number. Consignment keeps parts off your balance sheet as inventory, freeing working capital and improving your inventory turnover ratio because the counted stock you own is smaller relative to consumption.

VMI improves availability and reduces your ordering effort, but the parts are usually your asset the moment they land, so they sit on your books like any other purchased inventory.

This matters most for high-value, low-frequency items: a spare motor, a servo drive, or a gearbox that you must have on hand but may not touch for two years. Financing that shelf yourself is expensive idle capital.

Worked example: a critical drive spare

Assume you keep 20 critical spares averaging 3,000 EUR each, so 60,000 EUR of stock, and you consume about 8 of them per year. Your internal cost of capital plus storage and insurance runs 18% annually.

1. Owned or VMI stock: You carry the full 60,000 EUR. Annual carrying cost is roughly 60,000 x 0.18 = 10,800 EUR, incurred whether or not the parts move.
2. Consignment stock: The supplier owns the 60,000 EUR shelf. You pay only as you consume. On average you hold about half the value as work-in-transit ownership at any point, so your carrying cost falls to roughly 30,000 x 0.18 = 5,400 EUR, and you free up around 60,000 EUR of cash that was previously locked in unused iron.

The consignment route saves roughly 5,400 EUR per year in carrying cost here and, more importantly, releases capital you can deploy elsewhere. The trade is that suppliers price consignment risk into unit cost, so you validate that the per-part premium is smaller than the carrying saving before signing.

Risk allocation: obsolescence, shrinkage, and stockouts

Every stocking model moves three risks around. Deciding who should hold each is the real negotiation.

• Obsolescence risk: Under consignment this stays largely with the supplier, since they own parts that may never sell. Under VMI it shifts to you once goods are delivered, so an engineering change that retires a component leaves you holding dead stock.
• Shrinkage and counting risk: With consignment you must report consumption accurately and protect stock you do not own, which raises the bar on CMMS discipline. Miscounts become disputes over someone else's asset.
• Stockout risk: VMI is built to attack this. Because the supplier watches usage and owns the replenishment decision, availability tends to improve for the parts inside the program. Consignment alone does not guarantee this unless replenishment rules are also written into the deal.

A useful discipline is to run an ABC analysis across your parts catalog first, then match the model to the class. High-value A-items with unpredictable demand are strong consignment candidates. High-frequency C-items where the pain is administrative effort are natural VMI candidates.

Which parts suit which model

The models are not rivals so much as tools for different segments of your storeroom. A practical split:

• Lean toward consignment for: expensive, insurance-type spares tied to condition based maintenance triggers, long-lead items you must stage on site, and anything where you want the supplier to carry obsolescence.
• Lean toward VMI for: high-turnover consumables, fasteners, filters, seals, and lubricants where the value of the deal is eliminating manual reordering and keeping your reorder point and safety stock tuned automatically by the vendor.

Both models depend on trustworthy consumption data. If your issued-parts records are noisy, a supplier managing your replenishment will over- or under-stock, and a consignment count will drift out of agreement. Clean usage history from your maintenance system is the shared prerequisite, and it feeds directly into your reliability metrics and downtime analysis.

Contract terms that prevent disputes

Whichever model you pick, write these terms down before the first pallet arrives:

1. Ownership transfer point: exactly when title passes (consumption, delivery, or a fixed aging window).
2. Consumption reporting cadence: how and how often you confirm usage, ideally a direct feed from your work-order system.
3. Min and max levels: the replenishment envelope, reviewed on a set schedule as your equipment mix and OEE priorities change.
4. Aging and obsolescence: what happens to consigned stock that sits untouched past an agreed period, and who absorbs write-offs.
5. Reconciliation rights: joint physical counts and how discrepancies are resolved.

Where Fabrico fits

Consignment and VMI both live or die on the accuracy of one number: what you actually consumed. Fabrico is the real-time data foundation that produces that number. Its field-ready CMMS ties spare-part issues to specific work orders and assets, so every part drawn from a consigned shelf or a VMI bin is logged against the job that used it, giving you a defensible consumption record for supplier reconciliation.

Because Fabrico also captures real-time OEE and production monitoring (including computer vision on machines that have no PLC), you can connect part usage to the equipment and downtime events that drove it, which sharpens the min and max levels you negotiate.

Preventive scheduling means predictable demand your supplier can plan against instead of guessing. Fabrico is EU-built with EU data residency. It does not perform automatic reordering itself, but it gives your team and your suppliers the clean, current usage data that makes either stocking model trustworthy.

Frequently Asked Questions

Can you use consignment and VMI together?

Yes, and many mature maintenance stores do. You can have a supplier both own the stock (consignment) and manage its replenishment (VMI) in a single agreement. The key is to state the two mechanics separately in the contract: ownership and payment timing under the consignment clause, and replenishment decision rights and min and max targets under the VMI clause, so neither is left ambiguous.

Which model is better for expensive critical spares?

Consignment usually wins for high-value, low-frequency insurance spares because it keeps large sums of capital off your balance sheet and shifts obsolescence risk to the supplier. VMI shines for high-turnover consumables where the main benefit is removing manual reordering effort. Segment your catalog with an ABC analysis and apply each model where its strength matches the part's profile.

What data do suppliers need to run either model well?

Reliable, timely consumption data tied to assets and work orders. Suppliers set replenishment levels and reconcile consigned stock from your usage history, so noisy or manual records lead to over-stocking, stockouts, and disputes. A CMMS that logs every issued part against a specific job, and links it to equipment usage, gives both sides a single source of truth.

Ready to build the accurate spare-parts consumption record that makes consignment and VMI actually work? Book a Fabrico demo to see how real-time OEE and a field-ready CMMS give you and your suppliers one trusted view of usage.