Customer Concentration Risk: What Ontario Business Buyers Should Watch For

When you're evaluating a business to buy in Ontario, the income statement can look healthy while hiding a structural problem: too much of that revenue may come from too few customers. Customer concentration risk is one of the most common reasons a seemingly profitable business turns out to be far more fragile — and far riskier to finance and price — than its numbers first suggest.

This isn't a defect that shows up on a balance sheet. It surfaces only when you ask the right questions during due diligence, read the underlying contracts, and think through what happens to the business the day one major customer decides to leave.

This article explains why concentration matters, how to investigate it properly, and how buyers typically address it in the deal itself rather than simply walking away.

Why Customer Concentration Matters to a Buyer

A business that earns most of its revenue from a small number of accounts is, in effect, several smaller and much less diversified businesses stacked together. If one of those relationships ends — through non-renewal, a change of ownership on the customer's side, a pricing dispute, or simple attrition — the impact on cash flow can be immediate and severe.

Concentration risk affects a buyer in several practical ways:

• Financing. Lenders scrutinize customer concentration closely, since a loan secured against future cash flow is only as reliable as the customers generating it.
• Valuation. Earnings tied to a handful of relationships are generally considered lower quality than the same dollar amount spread across many customers, because the risk of losing them is harder to diversify away.
• Post-closing risk allocation. If a key customer leaves shortly after closing, the buyer — not the seller — usually bears that loss, unless the purchase agreement says otherwise.

None of this means a concentrated business can't be bought successfully. It means the risk needs to be identified, investigated, and reflected in how the deal is priced and structured.

How Concentration Shows Up in Due Diligence

Standard due diligence on a business purchase includes a review of material contracts, financial statements, and customer records — and this is where concentration risk becomes visible. A buyer, with their lawyer and accountant, should expect to:

• Request a revenue breakdown by customer over multiple years, not just the most recent one, to see whether concentration is growing, shrinking, or stable.
• Review the actual contracts, purchase orders, or ongoing arrangements with the largest customers — not just the seller's description of the relationship.
• Check for renewal dates, termination rights, exclusivity clauses, and any change-of-control language that could let a customer walk away specifically because the business is being sold.
• Ask how long each major relationship has existed, and whether it depends on a personal relationship with the seller rather than the business itself.

A relationship that depends heavily on the seller personally, rather than on the company's brand, pricing, or service, is a particular concern, because that goodwill may not transfer to a new owner at all.

Questions to Ask About Every Major Customer

• [ ] What share of revenue and gross margin does this customer represent, and has that share been rising or falling?
• [ ] Is there a written contract, and when does it expire or renew?
• [ ] Does the contract include a change-of-control or assignment clause that could be triggered by the sale?
• [ ] Who at the business holds the relationship — is it institutional, or tied to one person?
• [ ] Has this customer ever threatened to leave, renegotiated pricing aggressively, or been slow to pay?
• [ ] Would losing this customer alone put the business into a loss position?

Structuring the Deal to Reflect the Risk

Buyers rarely solve concentration risk by simply asking for a lower price and leaving it there. It's more common to address it through the mechanics of the purchase agreement itself:

• Holdbacks or escrows. A portion of the purchase price can be withheld for a defined period after closing, giving the buyer recourse if a key customer leaves shortly after the sale.
• Representations and warranties. The seller can be asked to confirm, as a term of the agreement, that no major customer has indicated an intention to reduce or end its business, backed by an indemnity if that turns out to be false.
• Price adjustments. Some deals tie part of the price to post-closing performance rather than paying everything upfront, so the buyer isn't fully exposed if concentration risk materializes immediately.
• Direct outreach. Where the seller agrees, a buyer may want to speak with a key customer, carefully and usually only late in the process, to gauge whether the relationship will continue under new ownership.

None of these tools eliminate the risk entirely — they allocate it more fairly between buyer and seller than a simple handshake would.

Does It Matter Whether You're Buying Assets or Shares?

Concentration risk itself doesn't disappear in either structure — the business still depends on the same customers. But the two structures affect how existing customer contracts move with the deal. In a share purchase, the corporation itself doesn't change, so its contracts generally continue without needing third-party consent, unless a contract has its own change-of-control clause. In an asset purchase, contracts often need to be formally assigned to the buyer, which can itself trigger a customer's right to object or renegotiate — something worth checking early, not after the purchase agreement is signed.

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