How Buyers Actually Underwrite Customer Concentration
By Brian Cassidy, Business Broker
When one customer represents 30% of a company’s revenue, sophisticated buyers do not view that as a footnote.
They view it as a concentration of cash flow risk, and that distinction matters.
Why One Customer at 30% of Revenue Changes More Than Valuation
Sellers often frame a large customer as evidence of strength: a longstanding relationship, repeat business, trust, and revenue stability. Buyers may acknowledge all of that. But they are not underwriting the seller’s history. They are underwriting the durability of earnings after closing.
The buyer’s concern is not simply that a customer is “too large.” The concern is that a meaningful portion of EBITDA may be less durable, less transferable, and more vulnerable to disruption than the historical financials suggest. That is exactly why customer concentration is commonly evaluated as part of broader risk assessment in valuation and transaction work. (Mercer Capital)
At a Practical Leve, Concentration Changes the Buyer’s Internal Thought Process in Four Ways:
First, it forces a buyer to test whether the revenue stream is truly institutional or merely relational.
In other words: does the customer buy from the company, or do they buy from the owner? If the relationship is primarily tied to the founder’s personal credibility, responsiveness, or history, the buyer is not really acquiring a stable commercial asset. They are acquiring a transition problem.
Second, concentration introduces a repricing risk. A customer that represents 30% of revenue often has leverage whether they exercise it or not. Buyers know that a customer of that size can use a change in ownership to renegotiate pricing, service expectations, payment terms, or exclusivity. That means the risk is not limited to customer loss. The more subtle risk is margin compression after closing.
Third, concentration affects how buyers think about earnings quality. A concentrated customer base can make reported earnings appear stronger than they are if those earnings are supported by one unusually favorable relationship, one account with unusually low acquisition cost, or one customer whose retention has never really been stress-tested. Buyers are not just asking whether the revenue exists. They are asking whether it is repeatable on a portfolio basis.
Fourth, concentration creates financing friction. Even if a buyer is comfortable with the business, lenders may not be.
In leveraged transactions, concentration can affect underwriting because the lender is effectively asking a simpler question: what happens to debt service coverage if this one account weakens? That is one reason customer concentration often becomes a financing and structure issue, not just a valuation issue. (Divestopedia)
This is why sellers are often surprised when a buyer says, “We still like the company, but we need to solve for this.”
That phrase matters.
Because in most transactions, customer concentration does not necessarily kill value — it changes how value is delivered.
A buyer may not immediately reduce the headline purchase price. Instead, they may reallocate risk through structure. That often shows up as an earnout tied to customer retention, a seller note, a holdback, or a more extensive transition requirement. In effect, the buyer is saying: if this customer is as durable as represented, the seller should be willing to get paid against that outcome. That is consistent with broader M&A practice, where realized value depends as much on certainty and structure as on headline multiple. (Divestopedia)
The good news is that customer concentration is often addressable, provided the seller approaches it the right way.
The first and best remedy is to reduce the concentration before going to market. That does not necessarily mean shrinking the major customer. It usually means growing around them. If the business can take a 30% customer down to 18% or 20% of revenue simply by expanding the rest of the book, the perceived risk profile changes materially.
The second remedy is to institutionalize the relationship. Buyers gain confidence when the major customer is tied to a system rather than a personality. That means multiple relationship owners, documented workflows, embedded operating dependencies, regular commercial cadence, and ideally some form of contractual or recurring framework. The more the customer relationship looks like an enterprise relationship instead of a founder relationship, the more transferable it becomes.
The third remedy is to present the account through a diligence lens rather than a sales lens. Sellers often talk about concentrated customers in narrative terms — “they’ve been with us forever,” “they love us,” “they’re not going anywhere.” Buyers do not underwrite sentiment. They underwrite evidence. The seller should be prepared to show customer tenure, revenue history, margin profile, order consistency, retention behavior, breadth of relationship, and whether the account has expanded or contracted over time.
And if concentration remains a legitimate concern even after all of that, then the final remedy is not denial. It is precision in deal design.
If the buyer’s real concern is the retention of one account, then the cleanest solution is often to isolate that risk and structure around it directly rather than allowing it to contaminate the valuation of the entire company. In many cases, a narrow and intelligent structural solution is far less expensive than allowing the buyer to broadly discount the business because they cannot get comfortable.
Customer concentration is not just a revenue issue. It is a question of risk transfer.
And in a sale process, businesses that preserve value are usually not the ones with no issues. They are the ones where the seller understands exactly how a buyer will underwrite those issues — and has already done the work to solve them before they become expensive.