A major client can feel like a milestone. One contract can fill the pipeline, lift revenue fast, and give a company room to hire, invest, or turn away the smaller jobs it used to need just to stay busy.
That looks like strength - until the balance starts to shift. Sales become easier to forecast, cash flow feels more visible, and the business seems more stable, but beneath that comfort, more and more of the company begins to revolve around one customer.
At what point does a great contract stop being a great deal? Is there a revenue share where dependence becomes dangerous, or do the real warning signs show up somewhere else? And should a company wait for the client to leave, or act before that happens?
Why a Major Contract Changes the Structure of Risk
Revenue concentration is not automatically a problem. For a young B2B company, one major customer can be a powerful growth engine: fewer sales calls, larger projects, longer planning horizons, and faster scale.
Even large public companies can rely heavily on a handful of customers. In 2025, two Arista Networks customers accounted for 26% and 16% of total revenue. Yet Arista continues to expand across enterprise markets in healthcare, manufacturing, education, oil and gas, and media.
TSMC shows a similar pattern. In its 2025 financial statements, its two largest customers represented 19% and 17% of revenue, respectively.
The point is simple: there is no magic line where a major customer suddenly becomes a threat. IFRS 8 uses 10% as the point at which a public company must disclose dependence on an individual external customer, but that is a reporting threshold, not a rule that says 9% is safe and 11% is risky.
What matters is what sits behind the percentage. A customer can represent 25% of sales while demanding little extra cost and giving the company time to keep growing. Or the same 25% can support dedicated staff, rent, equipment, and debt, making the business far harder to adjust if the contract disappears.
That is why revenue concentration should always be read alongside the cost structure. If a company hired people, bought equipment, expanded space, or built a separate division around one contract, those costs do not vanish when the client does. The more fixed costs tied to a single customer, the bigger the shock if the relationship ends.
It also helps to look at profitability, not just revenue. A big client can look impressive on paper while delivering thin margins and consuming most of the team's time. In that case, the customer may generate a large share of sales but a much smaller share of profit.
The first warning sign often appears in negotiations. The customer is still paying, the work is still coming in, and the relationship still looks healthy - but the company starts to realize how costly it would be to say no.
When the Client Gains Leverage Over the Terms
Negotiating power depends not only on contract size, but on how easily each side can walk away. If the customer is a major share of the supplier's revenue while the supplier barely affects the customer's own costs, the leverage is no longer equal.
That imbalance usually shows up slowly. The client asks for a bigger discount, extra work at the same price, looser return terms, more dedicated staff, or longer payment terms. Each request may sound reasonable on its own, but together they create a new problem: refusing could put too much revenue at risk.
U.S. auto parts manufacturer Dorman Products describes this relationship directly in its financial reporting. In 2025, two customers together accounted for approximately 40% of the company's sales. Dorman states that the concentration of its customer base gives major buyers the ability to negotiate lower prices, longer payment terms, additional discounts, allowances, returns, and other more favorable terms. The company also notes that these concessions can reduce profitability and require additional capital to finance operations.
In other words, the risk starts long before the contract is lost. A company can keep growing revenue while quietly giving away margin and control. The more it depends on keeping the deal alive, the harder it becomes to reject bad terms.
Payment terms deserve special attention. Large customers often pay weeks or months after the work is done, while the supplier still has to cover payroll, rent, taxes, materials, and contractors on time.
If one client accounts for a significant portion of accounts receivable, a delay in a single large payment can sharply affect cash flow. Cardinal Health, for example, reported that in fiscal 2025 CVS Health represented 30% of its revenue and 26% of gross trade receivables at year-end. In its reporting, the company specifically identifies the risk that a major customer could reduce purchases, fail to pay, decline to renew, or terminate its agreements.
In Dorman's case, extended payment terms contributed to higher accounts receivable and additional use of cash. To offset the pressure on cash flow, the company sells part of its receivables to financial institutions at a discount. In 2025, the value of these sales was approximately $1.39 billion, while related factoring expenses amounted to $58.3 million.
The same pattern shows up in smaller businesses, just at a smaller scale. If a customer produces one-third of revenue and pays in 60 days, the company must finance two months of payroll and other costs itself. If order volume rises at the same time, the working-capital burden can grow even faster than profit.
That is the paradox of a major contract: revenue goes up, the backlog grows, and yet cash becomes tighter. The issue is no longer sales volume - it is the gap between spending money and getting paid.
Over time, financial dependence can become strategic dependence. If a large share of the team spends years serving one customer, the company naturally learns that client's processes and starts shaping its product around those needs. That can be useful - until one customer begins influencing the roadmap and the company's new features stop mattering as much to everyone else.
At that point, losing the contract becomes even more expensive. The company would not only replace revenue; it would also have to rethink staffing, product direction, and internal processes built around one relationship.
What Happens When the Contract Ends
Even a long and successful relationship does not guarantee that a customer will stay. The client may reduce its budget, change leadership, merge with another company, bring the work in-house, close a business line, or discontinue the product for which it originally hired the supplier.
The supplier may have done nothing wrong. The real question is not whether conflict is likely - it is whether the business can survive a decision made entirely outside its control.
A useful example appears in the financial reporting of Forward Industries. In fiscal 2024, one major customer of its design division accounted for approximately 25.2% of consolidated revenue. In December 2024, the customer announced that it was discontinuing the insulin pump development program on which the contractor had been working. Forward Industries expected a material decline in revenue, recognized an impairment of the division's goodwill, and announced cost-cutting measures, including workforce reductions. The company also planned to seek additional financing and more flexible payment arrangements with a supplier.
Context matters here: Forward Industries was already reporting losses and a working capital deficit, so the loss of the customer was not the sole cause of its financial difficulties. Still, the case clearly demonstrates how concentration can amplify an existing vulnerability. When one program represents a quarter of revenue, its termination immediately affects forecasts, asset values, staffing levels, and financing needs.
That is why client dependence should be stress-tested before anything starts to slip. The question is not just, "What if our biggest customer leaves?" It is, "What would that actually do to the business?"
A vague 30% revenue drop is not enough. The company needs to know which costs disappear with the contract and which remain. How many employees can move quickly to other work? Which leases, equipment, or contractor commitments still need cash? How long does it usually take to win a customer of similar size, and does the company have enough reserves to cover the gap?
Accounts receivable should also be tested separately. If a major customer accounts not only for a large portion of sales but also for a comparable share of unpaid invoices, the scenario in which that client experiences financial difficulties may be more dangerous than a standard contract termination. The company simultaneously loses future orders and risks not being paid for work already completed.
The quality of the sales pipeline also matters. A business may assume that its dependence is temporary, but if the current workload has caused sales efforts toward other customers to nearly stop, replacing the contract quickly may be impossible. While a major client is providing enough work, acquiring new customers can feel like an unnecessary expense. A year later, the company may discover that it has no active pipeline and that its industry's sales cycle takes six or nine months.
That is why the safest client may sometimes be the one that looks stable enough to distract the company from diversification. A regularly renewed contract can quietly become a reason to postpone building the next source of revenue.
When It Is Time to Reduce Dependence
Diversifying the customer base does not mean giving up a large and profitable client simply to reduce its percentage in the company's financial statements. If the contract generates a healthy margin, the client's payment discipline is satisfactory, and the relationship helps the company develop valuable expertise, deliberately reducing that work may make little economic sense.
A smarter approach is to use the income from that client to build alternatives. While the main contract is still strong, the company has time to grow sales, enter new segments, and build reserves without rushing to replace lost revenue.
The first sign that this work is necessary is when losing the client would no longer be manageable through ordinary operations. If the company would need emergency layoffs, new debt, or a new order of the same size within weeks, the dependence is already too high.
A second important sign appears when the company starts regularly accepting economically unfavorable terms because it is afraid of losing the customer. A lower price, longer payment period, or additional service can all be normal parts of negotiation as long as the business can calmly evaluate their cost and say no. When the potential loss of the contract makes refusal practically impossible, the customer has gained bargaining power that can gradually erode the margin of the entire deal.
A third signal is structural. If most key employees, systems, or processes were built for one customer and cannot easily be reused elsewhere, concentration has become operational, not just financial. At that point, the business may need to adapt its product and processes before it can truly diversify.
Finally, the company should regularly calculate how long it would take to replace its largest customer. For a business with a short sales cycle, losing 20% of revenue may be unpleasant but manageable if new deals close every week. For a company where a major corporate contract requires a tender, testing, and several months of approvals, an even smaller share of revenue can represent a serious risk.
A better benchmark is not "How much revenue comes from one client?" but "What happens if that client disappears?" The company should know how much profit would fall, which fixed costs would stay, how much cash would be needed until sales recover, and what would need to happen in the first few weeks.
If that scenario leads to a manageable decline in profit, concentration may remain an acceptable part of the business model. If losing a single customer would require emergency layoffs, new debt, or an immediate reassessment of the entire strategy, diversification should have started earlier.
A major client can bring scale, speed, and stability for years. But that value is highest only when the company can still negotiate on its own terms and keep operating even if the relationship ends.
The real measure of customer-base maturity is not the number of clients. It is whether the business can keep a major customer, reject bad terms, or part ways with that customer without risking its own survival. That freedom is what turns a big contract from a liability into an advantage.
