Some of the most attractive small businesses on the market carry a hidden flaw: a large share of revenue comes from just one or two customers. The margins look great, the growth looks steady, and then you notice that a single client represents 40 percent of sales. If that customer leaves after closing, the business you bought is not the business you paid for.
Customer concentration does not have to kill a deal. It does, however, change how you should value the business, what you verify in diligence, and how you structure the purchase price. Creative financing tools are especially useful here, because they let buyer and seller share the risk instead of fighting over it.
There is no universal rule, but most lenders and experienced buyers start paying close attention when any single customer exceeds 10 to 15 percent of revenue, or when the top five customers exceed roughly half of revenue. Above 25 percent for one customer, concentration becomes a central issue in the deal rather than a footnote.
Look at concentration across several years, not just the most recent one. A customer that jumped from 8 percent to 30 percent in a single year may reflect a one-time project rather than a durable relationship.
Your due diligence checklist should include a dedicated section on major customers. The key questions:
A quality of earnings report can help quantify revenue and margin by customer and flag unusual trends.
Sellers are often reluctant to let buyers contact customers before closing, and for good reason: news of a sale can unsettle relationships. Still, for a customer representing a large share of revenue, a structured conversation is worth negotiating for. Common approaches include a joint call late in the process after the purchase agreement is substantially negotiated, a meeting framed around continuity and service, or a requirement that the customer sign a contract extension or consent as a closing condition.
If the seller refuses any customer contact on a heavily concentrated account, treat that as information and adjust your structure accordingly.
Concentration usually lowers the multiple a buyer is willing to pay, because future cash flow is less certain. It also affects financing. Many lenders, including SBA lenders, will ask harder questions, may require more equity or seller participation, and may apply a discount to cash flow tied to the largest customer when sizing the loan. Plan for this early so the capital stack does not collapse late in the process. The acquisition finance stack article explains how the layers of senior debt, seller financing, and equity fit together.
An earnout can link part of the purchase price directly to the retention of the major customer. For example, a portion of the price is paid over two years only if revenue from that customer stays above a defined threshold. This aligns the seller's incentive to support the relationship through the transition. The earn-out structure guide covers how to define metrics and avoid disputes.
A seller note paid over several years gives the buyer a natural buffer. The purchase agreement can include a right to offset payments if the key customer terminates within a defined window for reasons related to pre-closing issues. Offset rights require careful drafting and legal review, but they are a common tool in concentrated deals.
A portion of the price can be held in escrow and released only after the major customer renews or stays active for a set period. See the article on escrow and holdbacks for how these are typically structured.
If the seller owns the relationship personally, negotiate a longer and more specific transition period, including joint meetings with the customer and a plan to move day-to-day contact to a named employee. A detailed seller transition agreement makes this enforceable.
The work does not end at closing. In the first 100 days, prioritize the major customer. Meet with them early, alongside the seller if possible. Ask what they value, what frustrates them, and what would make them expand the relationship. Avoid changing pricing, key contacts, or service levels in the first months unless the customer asks. At the same time, start a deliberate effort to diversify revenue so that concentration falls over time. Our guide to the first 100 days after an acquisition covers how to sequence these priorities.
Some concentration risk is too high to structure around. Consider walking away if the major customer has a short-notice termination right and has signaled dissatisfaction, if the relationship depends entirely on the seller who will not commit to a meaningful transition, or if the numbers only work assuming the customer stays forever. A good deal should survive a realistic downside case. For more frameworks on evaluating risk, see the Creative Acquisitions chapters and strategies.
Many buyers and lenders start focusing on concentration when one customer exceeds 10 to 15 percent of revenue, and treat it as a central deal issue above roughly 25 percent. The right threshold depends on contract strength and relationship durability.
Often yes, but it must be negotiated carefully and usually happens late in the process. For a heavily concentrated account, a structured conversation or contract extension as a closing condition is reasonable to request.
By tying part of the purchase price to continued revenue from the key customer, so the seller is paid in full only if the relationship holds through the transition.
Many will, but they typically look harder at contract terms and relationship history and may require more equity or seller participation. Discuss concentration with your lender early.
Meet the customer early, keep pricing and service consistent during the first months, move the relationship to a named employee, and start diversifying revenue over time.