The due diligence question most first-time buyers forget to ask

Happy Tuesday!

There’s one due diligence mistake I see first-time buyers make more than almost any other.

It's not about the financials, the valuation, or the management structure.

It’s failing to ask about customer concentration.

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What Customer Concentration Actually Means

Customer concentration refers to how a business’s revenue is distributed across its client base.

A business with 200 clients where no single one represents more than 2% of revenue is very different from a business with 10 clients where the top three are responsible for half the income.

The general rule of thumb: if any single client accounts for more than 10% of total revenue, that’s worth paying close attention to.

Why this Matters More Than Most Buyers Realize

Small business owners often build deep, long-term relationships with a handful of key clients, and quietly, over time, those relationships become the backbone of the entire operation.

From the outside, this looks like loyalty and stability, and in some ways, it is!

But it also means the business is one phone call away from a very different financial picture.

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I’ve seen deals where a single client was responsible for 70% of annual revenue.

The seller had worked with that client for over a decade and was completely confident the relationship would survive a transition.

The Math Gets Ugly Fast

For businesses in the $1M-$2M revenue range, the impact of losing a major client can fundamentally change whether the business can cover its debt service and operate normally.

At that size, you don’t have the revenue diversity to absorb a significant loss.

And if there’s no active pipeline replacing outgoing clients, you can find yourself in a very difficult position very quickly.

What to Look For

Before you go deep on any deal, ask for a revenue breakdown by client.

Find out what percentage of total revenue each client represents, how long they’ve been a customer, and whether their contracts renew automatically or require active renegotiation.

If the seller is hesitant to share that information, that’s also a signal worth paying attention to.

This is one of those questions that takes five minutes to ask and can save you from a very expensive mistake.

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