Customer Concentration Risk

What customer concentration risk is and why it matters

Customer concentration risk is the degree to which a business's revenue depends on a small number of customers. A business where one customer represents 40% of annual revenue is highly concentrated - if that customer leaves, 40% of revenue disappears immediately, and the SDE that justified your purchase price drops by a similar proportion.

SBA lenders assess customer concentration explicitly. Most preferred lenders flag concentration when a single customer exceeds 20–25% of annual revenue. Some lenders have internal guidelines that limit SBA loans for businesses with a single customer above 15%. Banks that push past 25% concentration typically require additional personal guarantee provisions, a larger seller note carryback, or a reduced loan-to-value.

For buyers, concentration risk affects both the valuation and the structure of the deal. A business with a 40% revenue concentration in one customer should trade at a meaningfully lower SDE multiple than an equivalent business with diversified revenue - typically 0.5–1.5x lower, depending on the concentration level and the nature of the customer relationship.

How to identify and measure concentration in due diligence

Request a customer revenue breakdown for the past three years - not just the trailing 12 months. Revenue can shift between customers annually, and a three-year view shows whether concentration is stable, improving, or worsening.

Calculate the Herfindahl-Hirschman Index (HHI) as a quick concentration score: sum the squares of each customer's revenue share as a percentage. A HHI below 1,500 indicates moderate concentration. Above 2,500 is highly concentrated. A single customer at 50% of revenue produces a HHI of at least 2,500 on that customer alone.

Ask for the contract status of the top three customers: are they on long-term contracts, on annual agreements, or on month-to-month arrangements? A top customer on a 3-year contract with a renewal option is a different risk profile than the same customer on a 30-day cancellation notice. A government contractor or Fortune 500 client on a multi-year contract can sometimes justify above-average concentration - but the contract assignment clause at sale matters.

Check the customer's financial health separately from the business you are buying. If your largest customer is a single family-owned business that itself is struggling, your concentration risk compounds.

Negotiating price and deal structure for concentration risk

Customer concentration risk should be reflected in either the purchase price, the deal structure, or both.

Price reduction: A business with >25% single-customer concentration in an uncovered, month-to-month arrangement should trade at a 0.5–1.0x SDE discount relative to a comparable diversified business. Present this as a valuation argument, not a negotiating tactic: the multiple you pay reflects the risk-adjusted earnings, not just the current SDE level.

Earn-out provision: Structure a portion of the purchase price (typically 10–20%) as an earn-out contingent on the concentrated customer renewing or continuing after close. The seller, who has the relationship with that customer, should be incentivized to support the transition. An earn-out tied to Year 1 customer retention is a direct hedge against concentration risk.

Seller note tied to customer retention: A seller note where the interest rate or principal reduction is tied to the concentrated customer's revenue in Year 1–2 creates a shared risk structure. If the customer leaves, the seller absorbs part of the financial impact through note adjustments.

Transition support requirement: Require the seller to facilitate introductions to the top 3 customers - not just email introductions, but in-person meetings where the seller personally endorses the transition. This is often more valuable than any contractual provision.

See also: Working Capital Peg: What Buyers Miss at Closing - concentration risk directly affects the SDE that justifies the peg - and the SMB Due Diligence Checklist for the full customer revenue breakdown request.

Frequently Asked Questions