Vendor-managed inventory
Supplier-led replenishment, its distinction from consignment, and the stock, demand and service assumptions behind a VMI program.
Tags: sourcing, purchasing, inventory, replenishment
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In vendor-managed inventory (VMI), the supplier manages replenishment using agreed demand and inventory information. SAP also calls this supplier-managed inventory (SMI). Its guide uses demand, inventory on hand and agreed minimum and maximum levels as inputs. SAP, Supplier Guide to SAP Business Network for Supply Chain, pp. 120–121
Worked example: replenishment quantity versus available stock
With 420 on hand, 200 incoming and a target of 1,000, replenish 380 pieces in this example. The policy counts usable stock plus confirmed incoming supply. It assumes immediate review and no backlog, other commitments or rejects.
| Quantity at review | Pieces |
|---|---|
| Usable on hand | 420 |
| Confirmed incoming, arriving in two working days | 200 |
| Inventory position before a new order | 620 |
| Target inventory position | 1,000 |
| New replenishment quantity: 1,000 − 620 | 380 |
Counting only the 420 on hand would lead to a 580-piece order, overshooting the target by the 200 already incoming.
Assume consumption is exactly 100 pieces per working day and the existing 200-piece receipt arrives at the start of Day 3. On-hand inventory falls to 220 after two days, rises to 420 on receipt, and reaches 120 after Day 5. If the new 380-piece order arrives at the start of Day 6, stock rises to 500. Conservation reconciles the result: 420 opening + 200 received + 380 received − 500 consumed = 500 pieces.
If the new receipt instead arrives at the start of Day 8, Day 6 leaves 20 pieces and Day 7 demand exceeds available stock by 80. The same order quantity therefore supports different outcomes depending on arrival timing. This deterministic example contains no demand distribution and establishes no stockout probability or service-level guarantee.
Management, ownership and location are different dimensions
VMI does not necessarily mean consignment. In SAP’s terminology, stock owned by the supplier until customer consumption is consigned; stock owned by the customer on receipt is non-consigned. Both can participate in supplier-managed replenishment. The physical location of a bin therefore does not identify its owner. SAP, Supplier Guide, p. 120
The following comparison is explanatory synthesis rather than a standard contract definition:
| Dimension | Question it describes | What it does not establish by itself |
|---|---|---|
| Replenishment responsibility | Who determines or initiates the replenishment? | Ownership or invoice timing |
| Ownership | Who owns goods at a defined event? | Who counts bins or schedules deliveries |
| Physical custody | Where are goods stored and who can access them? | Their accounting treatment or availability for use |
| Commercial coverage | Which items, prices and services belong to the arrangement? | Unlimited supply or permission to substitute parts |
Payment dates, liability for damage, obsolete stock and end-of-program inventory are separate commercial subjects. The label “VMI” alone does not settle them. Similarly, a cabinet inside a factory may contain supplier-owned stock, customer-owned stock or separately controlled groups of each.
Bins, vending and information signals
VMI can connect industrial fasteners, production components or maintenance supplies to their point of use. Würth Industry USA, for example, describes a service that monitors materials at the customer facility and uses collected data to schedule deliveries and adjust stock levels. That is a named service model, not evidence that every VMI contract includes the same coverage or service frequency. Würth Industry USA, Custom Vendor Managed Inventory Programs
Würth describes two-bin Kanban for fasteners and other direct materials, with barcode or RFID identification and captured bin movements. Its vending offering addresses indirect materials such as maintenance and safety supplies. These examples show different ways of observing inventory movement; they do not make Kanban and VMI synonyms. Kanban describes a replenishment signal, whereas VMI describes management responsibility. Würth Industry USA, Inventory Management Solutions
Grainger’s KeepStock portfolio includes customer-managed inventory, Grainger-managed inventory and dispensing machines, subject to customer eligibility and agreements. Consequently, a managed-inventory product name or the presence of a dispenser does not alone identify which party performs replenishment. Grainger, Procurement Solutions, KeepStock section
The following limitations follow from the information represented by those signals. A recorded withdrawal may represent issue to a worker rather than actual consumption in a finished product. An empty-bin signal conveys a replenishment need but not necessarily the remaining quantity in another location. An overdue receipt can remain in an electronic pipeline even though it will not arrive before demand occurs. Inventory visibility is therefore useful only within the meaning, timing and coverage of its measurements.
Replenishment logic and its limits
SAP’s documented example shares demand and stock information between buyer and supplier and communicates planned shipments. This demonstrates that VMI involves information about future requirements and supply, not simply a count of what is visible today. It is a software-specific illustration, not a requirement to use SAP or a particular electronic message. SAP, Supplier Guide, pp. 120–121
An explanatory replenishment model can distinguish usable on-hand inventory, incoming supply, committed demand and buffer stock. A maximum level is a planning target under a chosen model, rather than proof that all demand up to that quantity can be met. Supply timing matters: 500 pieces arriving next month cannot satisfy a requirement tomorrow. Quarantined, damaged or incorrect-revision pieces may physically occupy storage while contributing nothing to usable availability.
Review frequency and delivery lead time also interact. A system observed weekly can consume stock between observations before a new replenishment even starts. Variable demand, delayed transport and pack-size constraints change the inventory needed to support a given service objective. No universal minimum, maximum or two-bin quantity follows from the VMI label.
Performance and source boundaries
Reduced ordering effort, fewer shortages and lower stock are different possible outcomes. A lower customer-owned inventory value can result from changed ownership without an equivalent reduction in physical stock. A larger buffer can improve availability while increasing space and exposure to obsolescence. These relationships explain why one headline savings figure cannot describe every dimension of a VMI arrangement.
The cited SAP PDF identifies itself on its cover as Document Version 2511 – 2025-12, ©2025; its definitions and workflow belong to that edition. The Würth and Grainger service pages display no issue date in the material reviewed on November 2, 2026. Their descriptions illustrate available program structures, not independently measured performance or the terms of a particular customer agreement.