A business with fifty customers and a business with one customer representing sixty per cent of turnover can show the same top-line revenue on the same day. Only one of them may be a bad meeting away from a very different year.
Concentration risk rarely appears in the numbers most manufacturers review each week: revenue, margin and order book. It sits behind them, in a question fewer directors can answer without checking:
How much of what we make, earn or deliver depends on one relationship or programme that could change without much warning?
That relationship is not always a customer. It may be a sole-source supplier for a critical component, material or process. It may be one vehicle platform, aircraft type or product programme around which the business has quietly built its machinery, tooling, skills and headcount.
Concentration is not automatically a mistake. A major customer or specialist supplier may be the reason a manufacturer has grown. The risk is carrying that dependency without measuring it, stress-testing it or deciding deliberately that the return justifies the exposure.
The percentage is only the beginning
Customer concentration is often measured as a share of turnover. That matters, but it can hide the real exposure.
A customer representing twenty per cent of revenue could contribute a much larger share of profit. It may also account for a disproportionate amount of receivables, work in progress, dedicated stock or specialist capacity. Losing it could therefore affect cash, earnings and operational utilisation at the same time.
Supplier concentration can be even less visible. A component may represent a tiny proportion of purchasing spend yet be capable of stopping an entire production line. Programme concentration may cut across several customer accounts while still depending on the same end platform, specification, approval or purchasing decision.
The useful question is not simply, “What percentage sits with the largest name?” It is:
Which single customer, programme, supplier or input would create the greatest operational or financial impact if it became unavailable for 30 days?
How growth creates concentration by accident
Concentration often begins as good news.
One account grows faster than the rest of the customer book. It wins more capacity and management attention. New machinery is justified by its forecast demand. Recruitment, shifts and working capital follow. Two or three years later, the account represents a level of dependency no one explicitly decided to accept.
The same pattern can develop upstream. A trusted supplier performs well, receives a growing share of spend and becomes embedded in drawings, approvals and production routines. An alternative may exist in theory, but nobody has checked whether it can meet the specification, volume, lead time or customer-approval requirements in practice.
Concentration has then become part of the operating model—not because the board chose it, but because a sequence of individually sensible decisions accumulated into one dependency.
If the largest customer changes course
The effect of losing or reducing a major customer is rarely proportional to its share of turnover.
Revenue can disappear faster than wages, rent, finance repayments and other fixed costs can be reduced. Dedicated stock and work in progress may become difficult to recover. Machinery or tooling purchased for the account may have limited alternative use. A customer representing forty per cent of turnover can therefore create an impact greater than forty per cent of operating profit or cash generation.
The trigger does not have to be insolvency. Orders may be paused, a contract may be re-tendered, production may move to another site, a platform may be delayed or the customer may bring a process in-house. Contractual notice and practical warning are not always the same thing.
If the critical supplier fails
A sole-source supplier creates the mirror image of customer concentration.
If a critical material, component or outsourced process is unavailable, output may stop even while the manufacturer’s order book remains healthy. The business may know the name of an alternative supplier without knowing whether that supplier can actually deliver.
A credible alternative may require technical qualification, new tooling, customer approval, revised transport arrangements or minimum order commitments. It may also rely on the same upstream producer, region, port, technology or material as the original supplier. Two supplier names do not necessarily mean two independent sources.
The UK Government’s recent supply-chain resilience work emphasises that vulnerabilities sit across networks, including shared suppliers, geographic clusters and upstream chokepoints—not only in the direct supplier relationship.
If the programme ends
Programme concentration can be harder to see because it may be spread across purchase orders, customer entities and individual part numbers.
A manufacturer may supply several Tier 1 customers whose demand ultimately depends on the same vehicle platform, aircraft programme or end product. At customer level the book looks diversified. At programme level it is not.
Capacity, tooling, approvals and specialist knowledge built around one programme may have limited value elsewhere. End of life, re-competition, redesign or a change in build rate can turn a decision made elsewhere into idle capacity, a tooling write-off and a sudden gap in contribution.
Warning signs
- No one can state, without checking, what percentage of turnover and profit sits with the largest customer or programme.
- Growth over the last two or three years has been driven overwhelmingly by one account without a deliberate decision to accept the dependency.
- A critical input or process relies on a single supplier with no tested alternative.
- Capacity, tooling or headcount has been built around one customer programme with no plan for end of life, re-competition or reduced volume.
- Trade-credit exposure to the largest customer or debtor is not actively monitored and the available protection has not been reviewed.
- Supplier alternatives have been named but not qualified, sampled or tested at the required volume.
- Contracts with the largest customer or supplier have never been reviewed outside the commercial team managing the relationship.
- Apparently different suppliers depend on the same upstream source, geography, logistics route or technology.
Six questions for the board
- What percentage of turnover, gross profit and receivables sits with our largest customer—and how has that changed over the last three years?
- If that customer paused or halved orders tomorrow, how long could we sustain the present fixed-cost base and remain within any covenant obligations?
- Is there one supplier, material or outsourced process whose loss would stop production, and have we tested a genuinely independent alternative?
- Are we carrying uninsured or insufficiently monitored credit exposure to a customer whose non-payment would materially affect cash?
- Has one programme or platform left us holding capacity, tooling or specialist skills with limited value beyond that relationship?
- Would our lender, credit insurer, investor or prospective buyer see the concentration differently from the way we describe it internally?
Five actions to take now
- Map the concentration. Calculate the share of turnover, gross profit, receivables, work in progress and dedicated capacity attached to the top customer, supplier and programme.
- Stress-test the loss. Model a 30-day interruption and a sustained fifty per cent reduction in demand against cash, fixed costs, covenants and recovery options.
- Test the alternative. For every critical sole-source dependency, confirm specification, approval, volume, lead time and upstream independence—not merely the name of another supplier.
- Review the financial protection. Examine credit limits, payment terms, trade-credit protection, contractual rights and the cash consequence of non-payment or cancellation.
- Choose the response deliberately. Accept, reduce, diversify, transfer or prepare for the concentration, with an owner and review date for the chosen action.
The InduX view
Concentration is not a reason to reject a valuable customer, abandon a strong programme or duplicate every supplier. It is a reason to understand what the business has become dependent on.
The most dangerous concentration is often not the largest percentage on a spreadsheet. It is the dependency that combines high impact, slow replacement and weak visibility—and which the business has never tested because the relationship has always worked.
Start with one question:
Which single customer, programme, person, system, supplier, material or geographic source would create the greatest operational or financial impact if unavailable for 30 days?
Then follow the dependency through revenue, production, cash, capacity, people, contracts and recovery. That is how a percentage becomes a decision.
Sources and further reading
- Global Supply Chains: A Foresight Report on Risk and Resilience — UK Government
- Supply Chain Guidance for Business — National Protective Security Authority
- How to insure against non-payment when exporting — UK Export Finance
This article provides general information and prompts for management discussion. It is not legal, financial, insurance or other professional advice. Appropriate specialist advice should be obtained for the circumstances of the business.