Written by Julien Ricciarelli-Bonnal
14 October 2026
The Essentials
Winning a customer that represents 30, 40 or even 50% of revenue can transform a small business. The contract can fund recruitment, support investment and give the company credibility it would otherwise take years to build. But the larger the account becomes, the more commercial power shifts towards the customer. A pricing negotiation, delayed project, internal restructuring or sudden loss of the contract can then affect the entire organisation. The danger is not having a large customer. It is becoming unable to operate without one. The most sensible response is rarely to shrink a successful relationship, but to use the growth it provides to build other sources of revenue.
Most business owners would welcome the contract that suddenly changes the scale of the company. A large account arrives, revenue jumps, capacity fills and decisions that previously looked too risky become possible. The company recruits, invests in systems or equipment, becomes more credible with suppliers and may find that other prospects take it more seriously simply because a major organisation has already trusted it.
During that period, customer concentration barely feels like a problem. Asking whether the new account generates too much revenue can sound strangely pessimistic when the commercial team has spent years trying to win exactly this kind of opportunity. As long as the customer buys regularly, pays on time and remains satisfied, concentration looks like success rather than vulnerability.
The difficulty is that dependency develops before anything goes wrong. It begins when staffing, investment, cash requirements and sometimes even the company’s product or service structure start being organised around revenue whose continuation ultimately depends on somebody else’s decisions.
There is no magic percentage at which a customer becomes dangerous
It is tempting to create a simple rule. Perhaps no client should represent more than 20%, 30% or 40% of revenue. Such thresholds can be useful warnings, but they cannot describe the actual risk on their own. A customer responsible for 40% of revenue under a stable multi-year agreement is not equivalent to one responsible for 25% through orders that can disappear from one month to the next.
The company’s financial structure matters just as much. A business with substantial cash reserves, limited fixed costs and a healthy pipeline of opportunities can absorb a reduction far more easily than a company that recruited an entire team specifically to service one account. Revenue concentration tells management where exposure sits, but dependency is determined by what has been built around that exposure.
Margin also changes the picture. A large customer that produces impressive revenue while requiring substantial discounts, bespoke work and disproportionate attention may contribute much less economic value than its headline number suggests. The organisation becomes busy, capacity appears fully utilised and turnover looks reassuring, while relatively little of that activity is actually strengthening the company.
A more useful stress test is therefore not simply to ask what percentage of revenue the customer represents. Ask what would happen if its spending fell by half tomorrow. If the immediate consequences include redundancies, cash pressure, stranded investments or an inability to cover fixed costs, customer concentration has become a structural issue.
Negotiating power changes when the customer knows you need them
A relationship can remain excellent while the balance of power gradually shifts. The larger an account becomes, the stronger its negotiating position is, even when the customer has no intention of exploiting the situation. A request for a larger discount, longer payment terms or additional work has a completely different significance when saying no could place 5% of revenue at risk than when it could affect 45%.
Over time, this can change how the supplier behaves. Exceptions become easier to approve, urgent work is absorbed without being fully charged, price increases are postponed and resources are diverted from other accounts because keeping the largest customer satisfied appears more important than almost anything else. The contract can remain profitable while its economics slowly deteriorate.
The mechanism is similar to other forms of commercial dependence. A sales channel can remain profitable while becoming strategically dangerous because the business gradually loses credible alternatives. The same applies to a customer. Success is not the problem. The problem appears when the company can no longer realistically choose to refuse terms that weaken its position.
Customer power can also reshape the business itself. A major account asks for a specialised feature, a bespoke process or a different service model. The request looks entirely rational because the customer funds so much of the organisation. Then comes another request and another. Several years later, the company may discover that part of its operation has effectively been designed for one client, even though those investments have limited value elsewhere in the market.
A major customer can disappear without anyone doing anything wrong
It is reassuring to imagine customer concentration as a relationship-management problem. If the company delivers excellent work, communicates properly and keeps the customer happy, perhaps the revenue is safe. Unfortunately, some of the biggest reasons for losing an account sit completely outside the supplier’s control.
The customer may be acquired. A new chief executive may arrive. Budgets can be cut, procurement centralised, a project cancelled or a function brought in-house. A local subsidiary can lose purchasing autonomy because headquarters decides that every country must now use one global provider.
An excellent supplier can therefore lose an excellent customer without having failed in any meaningful sense. That is what makes concentration risk fundamentally different from ordinary customer satisfaction. A substantial part of the company’s future has been attached to decisions made in another organisation.
The change does not always arrive as one dramatic cancellation either. Spending may fall by 15%, another project moves into the next financial year, a product line closes and a recurring piece of work quietly disappears. Each reduction appears manageable, but together they expose how much of the company’s previous growth assumed that one relationship would remain unusually stable.
Diversification should grow around the successful client, not against it
Once management recognises the risk, deliberately shrinking a healthy account is usually the wrong response. There is little sense in rejecting profitable business purely to improve the appearance of a customer concentration chart. The better objective is to make the rest of the portfolio grow faster.
Imagine a customer generating £500,000 in a business with £1 million in annual revenue. It accounts for 50%. If the company retains the entire account but adds another £500,000 from other customers, concentration falls to one third without sacrificing any existing revenue. The healthiest diversification is usually additive.
This sounds obvious, but operational success often works against it. When the order book is already full, business development feels less urgent. Management focuses on delivery, sales teams naturally give attention to the customer producing the most immediate revenue and prospecting activity becomes something that can be restarted later.
Later is often the worst time to restart it. A strong strategy and business development approach that deliberately builds multiple segments, routes to market and commercial opportunities makes diversification part of growth rather than an emergency response to a threatened account. The objective is not to accumulate customers for statistical comfort. It is to ensure that no single commercial relationship has the ability to destabilise the company.
More customers do not automatically mean less concentration
Diversification can also create a false sense of security. Winning several subsidiaries of the same corporate group may look like several new customers in the CRM, while the purchasing decision can still be changed by one central procurement team. Working with multiple distributors may appear diversified even though every one of them ultimately serves the same end market.
Customer concentration should therefore be examined alongside sector, geography, product, corporate ownership and acquisition channel. A company with fifty customers can remain highly exposed if 80% of them belong to the same industry. A downturn affecting that market may hit many accounts simultaneously, even though no individual customer appears dominant.
Contract structure matters too. Hundreds of one-off transactions are not automatically safer than a smaller number of well-distributed recurring relationships. Genuine resilience comes from reducing the number of events capable of damaging a large share of revenue at the same time.
This is why the customer count itself is a weak measure of commercial security. A business can have a long customer list and still depend on one sector, one product category, one introducer or one channel. Diversification is ultimately about independent economic engines rather than the number of names stored in a sales database.
The best time to reduce dependency is when the customer is still thriving
If the major customer announces that it is leaving, diversification instantly becomes an emergency. Sales teams are asked to replace a large amount of revenue quickly, management negotiates from a position of anxiety and the company may accept the first substantial contract available, recreating the same concentration risk with another account.
The ideal moment is almost the opposite. The relationship is healthy, revenue is strong and the cash generated by the customer is still available to finance business development. The company can test new segments, build visibility, strengthen sales capability and allow new opportunities enough time to mature instead of expecting them to replace lost revenue immediately.
Reducing dependency can even improve the existing customer relationship. A supplier that is financially secure is better able to negotiate sensibly, resist work that destroys margin and make decisions based on the long-term health of the partnership. When every disagreement threatens the survival of the business, neither side is operating within a particularly healthy relationship.
One major client is therefore not something a company should fear. For many SMEs, landing a large account is exactly what enables the next phase of growth. It can fund professionalisation, strengthen credibility and create opportunities that would otherwise remain inaccessible.
The danger begins when the company mistakes a highly successful commercial relationship for a permanent source of revenue. A resilient business does not avoid large customers. It builds itself so that even its largest customer remains a customer rather than a condition of survival.
Written by Julien Ricciarelli-Bonnal
14 October 2026
