Customer Concentration: How Much Revenue From One Client Is Too Much?

Every owner with a big client carries the same two sentences around: "they're a fantastic customer" and "if they ever left, we'd be in trouble." Both are true, usually in that order out loud and the reverse at two in the morning. Customer concentration is the most acknowledged unmeasured risk in small business: joked about, rarely quantified, almost never planned against. Quantifying it takes an afternoon, and the plan that follows doesn't require upsetting anyone.

What counts as too concentrated?

Start with the measurement, because gut feel is unreliable here. Take each customer's share of your rolling twelve-month revenue, then add up your top five together. Most owners have never done this on paper, and the result usually lands differently from the version they carry in their heads.

There's no legal limit and no magic number, but advisers, banks and acquirers work to a broadly shared convention: once a single client accounts for around a fifth of your revenue, they've stopped being a customer and become a strategic dependency you should be managing deliberately. Well beyond that, the honest description is that you're operating a division of their business that happens to have its own ABN.

Two refinements make the number truthful. Check profit concentration as well: a client whose share of your margin is much larger than their share of your revenue is a bigger exposure than the revenue figure admits. And check decision concentration: if three of your "customers" are subsidiaries of one group, share a procurement team, or all depend on the same end-market, they're one risk wearing several logos, and your spreadsheet should treat them that way.

The costs that arrive before any crisis

The catastrophe scenario gets all the attention, but concentration taxes you continuously while the relationship is going perfectly well.

• Pricing power inverts. Past a certain dependence, you stop setting prices with your biggest customer and start receiving them. The annual "partnership review" becomes a meeting where your margin is the agenda, and discounts that began as volume recognition harden into structure.
• The business shapes itself around them. Their systems, their formats, their reporting templates, their payment terms. Capability that should be market-facing becomes client-specific, and your best people end up effectively seconded.
• Decisions get taken hostage. Hiring, capacity and investment choices start being made to serve one relationship, which makes the dependency deeper each year it runs.
• Your options narrow. Lenders read concentration as credit risk, and acquirers respond to it with discounted offers or deal structures that shift the risk back onto you. You don't need to be selling to feel this; it shows up whenever you need outside confidence in the business.

How to reduce it without insulting the client

Diversification done badly reads as disloyalty, and the fear of that reading is why most owners never start. The answer is that you never shrink the big client; you grow around them.

Practically, that means ring-fencing business development capacity that the big client's demands cannot raid, because in a concentrated business the major account always wins the fight for attention unless someone has been made structurally unavailable to it. It means productising what serving that client taught you: the capability they paid you to build is usually your strongest pitch to the rest of their industry. And it means watching the mix of new revenue, which is where diversification shows up first, long before the overall percentages move.

Inside the account, spread the relationship across several contacts rather than one champion, and push for contract terms that buy you reaction time: notice periods, committed volumes, renewal dates you see coming. None of this offends anyone. Clients expect suppliers to have other customers; the ones who resent it are telling you something important.

The dependency audit worth pairing with this one

Concentration risk has a mirror image inside the business: the client may depend on one person at your end too, and if that person is you, the two risks compound. A business that can't run without its owner and can't run without its biggest customer has two single points of failure stacked on top of each other. The same discipline that maps client concentration applies to founder dependency, and fixing them together is what makes the growth durable rather than fragile. For the broader playbook on building revenue that doesn't lean on any single relationship, the Growth hub covers the channels side.

Run the numbers this week. The measurement costs an afternoon; the not-knowing costs you at 2am.