Where used function and Bill of material (BOM)

Where-Used Function in Procurement: How Buyers Use BOM Data to Understand Impact

A supplier informs you that a component will be delayed.

At first, it looks like one purchase order problem. But then the questions start.

Which products use this component?
Which production orders are affected?
Is the component used in only one assembly, or in several finished products?
Can we replace it with an alternative?
Which internal stakeholders must be informed?
How serious is the shortage?

This is the practical problem the where-used function helps solve.

For an operative buyer, the where-used function is not only an ERP feature. It is a way to understand impact. When a component, material, or part is affected by a delivery problem, quality issue, price change, engineering change, or supplier risk, the buyer needs to know where that item is used before deciding what to do.

The where-used function and the Bill of Material, often called the BOM, help the buyer connect one component to the wider product structure.

In this article, you will learn what the where-used function means, how it connects to BOM data, and how operative buyers can use it in daily procurement work.

LHTS classification

Role: Operative
Process: Order management, material planning support, inventory follow-up, delivery monitoring, change support, supplier issue handling
Level: Basic
Related course: Operative Buyer Processes

Quick answer: What is the where-used function?

The where-used function is an ERP or product data function that shows where a specific component, material, or part is used.

In procurement, it helps the buyer identify which products, assemblies, sub-assemblies, production orders, or planning structures depend on a certain item.

This is useful when the item has a delivery problem, quality issue, price change, supplier risk, or engineering change.

The problem the where-used function solves

Many procurement problems start with one item.

A supplier cannot deliver a component.
A part becomes obsolete.
A material price increases.
A quality deviation is discovered.
An engineering change replaces one component with another.
A supplier informs the buyer that lead time has increased.

The first question is usually simple:

What is affected?

Without a where-used view, the buyer may only see the direct purchase order or material number. That is not enough.

The real impact depends on where the component is used.

A small component can be used in several products.
A low-value part can stop an expensive production line.
A delayed material can affect multiple customer orders.
A design change can create purchasing consequences across many assemblies.
A supplier problem can become a production planning problem.

The where-used function helps the buyer see the connection between the component and the wider product structure.

It turns the question from:

“Is this item late?”

into:

“What does this late item affect?”

That difference is important.

What is a Bill of Material, or BOM?

A Bill of Material, usually called a BOM, is a structured list of the components, materials, parts, and sub-assemblies needed to make a finished product or assembly.

In simple language, the BOM is the product recipe.

It tells the organization what is needed, in what quantity, and often in which structure or level.

A BOM may include:

  • finished product
  • assemblies
  • sub-assemblies
  • components
  • raw materials
  • part numbers
  • quantities
  • units of measure
  • revision level
  • approved alternatives
  • source or supplier information
  • production or planning information

For procurement, the BOM is important because it connects what is designed, planned, purchased, stored, and produced.

If the BOM is wrong, procurement may buy the wrong quantity, the wrong revision, or the wrong component. If the BOM is correct, it supports purchasing, inventory planning, production planning, costing, and supplier follow-up.

What does the where-used function show?

The where-used function works in the opposite direction of reading a normal BOM.

A normal BOM starts with the finished product and shows which components are needed.

A where-used search starts with one component and shows where that component is used.

For example:

A normal BOM asks:
“What components are needed to build Product A?”

A where-used search asks:
“Which products use Component X?”

A where-used result may show:

  • finished products using the component
  • assemblies using the component
  • sub-assemblies using the component
  • quantity used per product or assembly
  • BOM level where the component appears
  • revision or version
  • plant or production site
  • active or inactive BOM status
  • related production or planning impact

This gives the buyer a practical impact map.

How this connects to the operative buyer role

The where-used function is especially useful for the operative buyer because the operative buyer often works close to daily order flow, delivery dates, inventory levels, supplier communication, and production needs.

When a supplier problem appears, the operative buyer is often one of the first people who must react.

The buyer may need to answer questions such as:

  • Is the component used in one product or many?
  • Is the affected item critical?
  • Do we have stock?
  • Which production orders may be delayed?
  • Which suppliers are connected to the item?
  • Is there an approved alternative?
  • Should the issue be escalated?
  • Which internal stakeholders need information?
  • Should we expedite, reschedule, or search for another source?

The where-used function does not replace buyer judgment. But it gives the buyer better information for making the right judgment.

A buyer who understands where an item is used can communicate more clearly, prioritize better, and avoid treating a critical issue as a minor problem.

Where this fits in the procurement process

The where-used function can support several parts of the operative procurement process.

It is especially relevant in:

  • purchase order follow-up
  • delivery monitoring
  • expediting
  • inventory management
  • shortage management
  • supplier issue handling
  • material planning support
  • engineering change support
  • cost change analysis
  • supplier risk assessment
  • production disruption prevention

It is also connected to MRP, or Material Requirements Planning.

MRP uses demand, inventory, lead time, and BOM information to calculate which materials are needed and when. The where-used function helps the buyer understand the product structure behind those requirements.

For the operative buyer, this means the where-used function is not only a technical master data tool. It is part of practical supply control.

Practical situations where buyers should use the where-used function

1. A supplier delivery is delayed

A supplier tells the buyer that a component will be two weeks late.

Before reacting, the buyer should check where the component is used.

If the component is only used in one low-priority product with enough stock, the problem may be manageable.

If the component is used in several high-volume products with low inventory, the issue may require immediate escalation.

The where-used function helps the buyer understand the seriousness of the delay.

2. A component has a quality problem

A supplier reports a quality deviation on a delivered part.

The buyer should not only check the affected purchase order. The buyer should also understand which products may include the component.

A where-used search can help identify affected assemblies or finished products. This supports communication with quality, production, engineering, warehouse, and supplier management.

3. A supplier announces a price increase

If one component becomes more expensive, the buyer needs to know where it is used.

A small price increase may have a large total impact if the component is used in many products or in high volumes.

The where-used function helps procurement understand whether the price increase is isolated or affects several product cost calculations.

4. A component becomes obsolete

Obsolescence is a common problem in manufacturing, electronics, spare parts, and technical procurement.

When a component is discontinued, the buyer must understand which products still depend on it.

The where-used function helps identify affected products, assemblies, and internal stakeholders. It also supports discussions about last-time buys, alternative components, redesign, or supplier changes.

5. Engineering changes a part

When engineering replaces, updates, or removes a component, procurement must understand what changes in the supply chain.

The where-used function can help identify the products affected by the change and support questions such as:

  • Do we still need to buy the old part?
  • What open purchase orders exist?
  • Is old stock still usable?
  • When should the new component be purchased?
  • Are suppliers informed?
  • Are prices, lead times, and minimum order quantities updated?

This helps avoid buying the wrong revision or creating obsolete stock.

6. The buyer needs to prioritize expediting

Expediting should be focused on what matters most.

If several components are late, the buyer can use the where-used function to identify which delayed items affect the most critical products or production orders.

This supports better prioritization.

The buyer can then spend time on the delivery problems that create the highest business risk.

7. The buyer needs to understand supplier risk

If a supplier is financially unstable, has capacity problems, or performs poorly, procurement needs to understand the impact.

A where-used analysis can show which products depend on components from that supplier.

This supports supplier risk discussions with tactical procurement, supplier management, production planning, and engineering.

A practical flow for operative buyers

A simple where-used working method can look like this.

Step 1: Identify the affected item

Start with the component, material number, part number, or supplier item that has a problem.

Make sure you are using the correct revision, plant, and unit of measure. Many mistakes start with checking the wrong item number or wrong version.

Use the ERP, PLM, or product data system to search where the component is used.

The result should show the products, assemblies, or sub-assemblies connected to the component.

Step 3: Check active and relevant structures

Not every result is equally important.

Some BOMs may be inactive, old, only used for spare parts, or connected to a product that is no longer produced.

Check whether the component is used in active products, current production, future demand, or service/spare part commitments.

Step 4: Understand quantity and demand

Check how many units of the component are needed per product or assembly.

Then connect this to current demand, open production orders, forecasts, stock levels, and purchase orders.

A component used once in a low-volume product has a different impact than a component used five times in a high-volume product.

Step 5: Check stock and open orders

The buyer should connect the where-used result to inventory and purchase order data.

Ask:

  • How much stock do we have?
  • Is the stock available or reserved?
  • Are there open purchase orders?
  • Are there delayed deliveries?
  • Are there alternative suppliers?
  • Are there approved alternative parts?
  • What is the lead time?

This turns the where-used result into practical procurement action.

Step 6: Identify affected stakeholders

Depending on the result, the buyer may need to inform:

  • production planning
  • warehouse
  • engineering
  • quality
  • supplier management
  • tactical procurement
  • customer service
  • project management
  • finance or controlling

The where-used function helps the buyer explain the issue with facts.

Instead of saying, “One part is delayed,” the buyer can say, “This component is used in three active products, two production orders are affected, and current stock covers only one week of demand.”

That is a much stronger message.

Step 7: Decide the action

The action depends on the impact.

Possible actions include:

  • expedite the supplier
  • split delivery
  • search for available stock
  • use an approved alternative
  • request engineering support
  • adjust production schedule
  • place an urgent order
  • escalate to tactical procurement
  • initiate supplier performance follow-up
  • update stakeholders with revised delivery information

The where-used function does not solve the problem by itself. It helps the buyer choose the right response.

Example: A delayed component used in several products

An operative buyer receives a message from a supplier.

A plastic housing component will be delayed by ten working days because of a tooling issue.

At first, the buyer sees only one open purchase order. The order quantity is not very large, so the issue may appear manageable.

Before accepting the delay, the buyer runs a where-used search.

The search shows that the component is used in four different finished products. Two of them are low-volume products, but two are connected to active customer orders and planned production next week.

The buyer checks stock and sees that inventory covers only three days of demand.

Now the issue is clearly more serious.

The buyer contacts production planning and confirms which production orders are affected. The buyer asks the supplier for a partial delivery and a recovery plan. The buyer also checks whether an approved alternative component exists.

Because the buyer used the where-used function early, the issue is escalated before production stops.

This is the practical value of the where-used function.

It helps the buyer see the real impact behind one component problem.

What operative buyers should check in a BOM

An operative buyer does not need to be a BOM engineer. But the buyer should understand enough BOM information to support daily procurement decisions.

Important BOM information for buyers includes:

  • component number
  • component description
  • quantity per assembly
  • unit of measure
  • revision level
  • approved alternatives
  • supplier or source information
  • plant or site
  • active status
  • effective date
  • scrap or yield factor, if relevant
  • lead time or planning data, if available
  • make-or-buy status
  • criticality of the component

This information helps the buyer avoid wrong assumptions.

For example, if a component is used in several BOM levels, the buyer must understand whether the total quantity needed is higher than it first appears.

If the BOM has several revisions, the buyer must make sure the purchase order matches the correct version.

If alternatives exist, the buyer must know whether they are technically approved and commercially available.

Common mistakes when using where-used and BOM data

Mistake 1: Looking only at the purchase order

A purchase order shows what has been ordered. It does not always show the full business impact.

The buyer should use the where-used function when the item may affect production, customers, cost, quality, or supply risk.

Mistake 2: Assuming one component means one product

Some components are used across many products and assemblies.

A small item may have a large impact if it is common across the product portfolio.

Mistake 3: Ignoring BOM revision

A component may be used in one revision but not another.

If the buyer checks the wrong revision, the impact analysis may be wrong.

Mistake 4: Forgetting inactive or future BOMs

The buyer should understand whether the component is used in active production, future products, service parts, or obsolete structures.

A component may not be needed for current production but may still be needed for spare parts or service commitments.

Mistake 5: Not involving engineering when alternatives are unclear

Buyers should not replace technical components without approval.

If an alternative part is not clearly approved, engineering or quality must be involved before the buyer acts.

Mistake 6: Not connecting where-used data to inventory

The where-used function shows where the component is used. It does not automatically tell the buyer whether enough stock exists.

The buyer must connect where-used information with inventory, demand, open purchase orders, and lead time.

Mistake 7: Treating BOM data as always correct

BOM data can be wrong, outdated, incomplete, or inconsistent between systems.

If the result looks strange, the buyer should verify with planning, engineering, production, or master data before making a major decision.

Where-used checklist for operative buyers

Use this checklist when a component, material, or part has a supply, quality, cost, or change issue.

  • What is the affected item number?
  • Is the revision correct?
  • Which products, assemblies, or sub-assemblies use the item?
  • Is the item used in active production?
  • Is the item used in spare parts or service commitments?
  • What quantity is needed per product or assembly?
  • What is the current stock level?
  • Is stock available or already reserved?
  • What open purchase orders exist?
  • What production orders or customer orders may be affected?
  • Is there an approved alternative?
  • Which supplier or suppliers provide the item?
  • What is the current lead time?
  • Who must be informed internally?
  • Is escalation needed?
  • Does the issue indicate a repeated supplier problem?

This checklist helps the operative buyer move from uncertainty to structured impact analysis.

How the where-used function supports better supplier communication

The where-used function also improves supplier communication.

When the buyer understands the impact, the buyer can communicate more clearly with the supplier.

Instead of saying:

“We need this part urgently.”

The buyer can say:

“This component is used in three active product families. Current stock covers four days of demand, and two production orders will be affected if the shipment is not received by Friday. Can you confirm partial delivery, revised shipment date, and recovery plan?”

That type of communication is more professional and more effective.

It shows the supplier why the issue matters and what information is needed.

It also helps the buyer decide when to escalate, when to expedite, and when to involve tactical procurement or supplier management.

How the where-used function supports supplier performance follow-up

Repeated problems with components found through where-used analysis can reveal supplier performance issues.

For example:

  • the same supplier repeatedly delays components used in critical products
  • the same component causes repeated quality deviations
  • lead time changes affect several product lines
  • cost increases affect many BOMs
  • supplier communication is too slow for high-impact items

This information should not stay only with the operative buyer.

It can support supplier performance reviews, category discussions, supplier development, alternative sourcing, and risk management.

The operative buyer plays an important role by making the operational impact visible.

The related Learn How to Source course bundle Operative Buyer Processes gives a structured foundation for the daily work of the operative buyer.

The where-used function is useful because it supports several operative buyer responsibilities: order follow-up, supplier communication, inventory understanding, delivery monitoring, and issue escalation.

If you want to strengthen your understanding of the operative buyer role, purchase orders, supplier interaction, and the practical procurement process, this course bundle is a natural next step.

FAQ: Where-used function and BOM for buyers

What is the where-used function in procurement?

The where-used function shows where a specific component, material, or part is used in products, assemblies, or sub-assemblies. It helps buyers understand the impact of supply, quality, cost, or design changes.

What is a Bill of Material?

A Bill of Material, or BOM, is a structured list of the components, materials, parts, and quantities needed to make a product or assembly.

Why is the where-used function useful for operative buyers?

It helps operative buyers understand which products and production needs are affected when one component has a problem. This supports prioritization, supplier communication, expediting, and escalation.

What is the difference between BOM and where-used?

A BOM starts with a product and shows which components are needed. A where-used search starts with a component and shows which products or assemblies use it.

When should a buyer use the where-used function?

A buyer should use it when a component is delayed, discontinued, changed, affected by quality problems, subject to a price increase, or connected to supplier risk.

Can the where-used function help with expediting?

Yes. It helps the buyer understand which delayed components are most critical and which deliveries should be prioritized.

Does the where-used function replace MRP?

No. MRP calculates material requirements based on demand, inventory, lead times, and BOM data. The where-used function helps the buyer understand where a component is used and what impact a problem may have.

Who owns BOM data?

BOM data is often owned by engineering, product management, manufacturing, or master data functions. Procurement uses BOM data but should verify unclear or suspicious data with the responsible function.

Can buyers change components based on where-used information?

No, not without approval. If a component replacement affects technical requirements, quality, safety, compliance, or product performance, engineering and quality must be involved.

Conclusion: The where-used function helps buyers see the real impact

The where-used function is a practical tool for operative buyers.

It helps the buyer move from a single component problem to a clear understanding of product impact, production risk, supplier exposure, and internal communication needs.

A delayed or changed component is rarely only a material number. It may be connected to several products, production orders, suppliers, and customer commitments.

By using BOM data and the where-used function correctly, the operative buyer can act earlier, communicate better, prioritize smarter, and support a more reliable procurement process.

In daily procurement work, that is the real value of the where-used function: it helps the buyer understand what is affected before deciding what to do next.

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