Agency client concentration
Client concentration is the share of your gross income coming from your largest client, and from your largest three. Above a third from one client, the account stops being a customer relationship and starts setting your pricing, your staffing and your risk. Measure it monthly, and treat a rise as a decision rather than a result.
Written for founder-led UK agencies of roughly £500k–£2M. Concentration builds during the good years, which is exactly when nobody raises it.
What concentration costs you
The risk everyone names is losing the account. The costs that arrive first are quieter: you discount to keep it, you staff around it, and you stop qualifying new work properly because the large client fills the gap.
You lose pricing authority
A client who knows they are a third of your income negotiates differently, and so do you. The discount rarely appears in a contract. It shows up as work absorbed without a conversation.
Your team shapes itself around them
Skills, seniority and process bend to one client's way of working. If the account goes, some of that capability does not transfer to the next one.
New business gets quieter
Pipeline effort falls when the revenue line looks comfortable. Concentration and a thin pipeline arrive together, which is what makes the loss so hard to absorb.
The agency becomes harder to sell
A buyer discounts concentrated income heavily, because they are buying one relationship rather than a book of business. It affects the price even if you never sell.
How to measure it
| Measure | How to calculate | What it tells you |
|---|---|---|
| Largest client share | Largest client's gross income over twelve months, divided by total gross income. | Your single largest point of failure. |
| Top three share | Same calculation for the top three combined. | Whether the risk is one relationship or a pattern. |
| Contracted forward income | Fees under contract for the next six months, split by client. | How much notice a loss would actually give you. |
| Relationship depth | Number of people at the client who would defend the relationship. | Whether the account rests on one contact who could leave. |
The last one gets missed most often. An account at 20% of income held by a single contact carries more risk than an account at 35% with four sponsors across two departments.
Reducing it without losing the account
Concentration falls in one of two ways: the denominator grows or the numerator shrinks. Growing the rest of the agency is the better route, and it takes two to four quarters, which is why the work starts before the number becomes uncomfortable.
Set a ceiling in advance. Agree the share at which you stop taking additional work from one client without adding elsewhere. A written number turns a difficult judgement into a rule.
Broaden the relationship inside the client. More sponsors, more departments, more than one person who would argue for keeping you. This reduces the real risk even when the percentage holds.
Ring-fence new business capacity. Protect the hours, with a named owner, so pipeline work continues through the busy quarters. This is the step agencies drop first and regret most.
Price the large account properly. Concentration and quiet discounting travel together, and the account is often your least profitable per hour. Check it against project and retainer margin before deciding it is worth the risk.
Common questions
What client concentration is too high for an agency?
Treat a third of gross income from one client as the point where it shapes your decisions, and set your own ceiling below it. The right number depends on how much contracted forward income you hold and how many sponsors defend the relationship. An account at 30% under a two-year contract with four sponsors is a different risk from 20% held by one contact on a rolling month.
Should we turn down more work from our biggest client?
Rarely. Take the work and use it to fund the correction: protect new business capacity, price the account properly, and broaden the relationship inside the client. Declining profitable work to improve a ratio weakens the agency while leaving the underlying dependency untouched.
How quickly can concentration be reduced?
Two to four quarters if you protect new business capacity from the start, since the fix is to grow the rest of the book while the big account stays where it is. Agencies that begin when the number is already uncomfortable take longer, because by then the pipeline has usually been thin for a year.
Does this matter if the client is happy?
Yes. Most large accounts are lost to something other than dissatisfaction: a change of marketing director, a budget cut, an acquisition, a review cycle. None of those are signalled by how the relationship feels, which is why concentration has to be measured: the relationship can feel fine right up to the cut.
Related reading: Fractional COO for agencies · Agency project and retainer margin · I'm the one selling and the one delivering · Agency WIP and payment terms
Put a number on the dependency
Bring your income split by client for the last twelve months. Concentration, contracted forward income and sponsor count together give a clearer read than any one of them.
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