I had a client that accounted for about 15% of our revenue. They were great to work with. Paid on time. Good briefs. Appreciated our work. And every single day, I was quietly terrified they would leave.
Because if they did, I would need to cut two members of staff within a month. There was no scenario where we absorbed a 15% revenue hit and kept the team intact. That one client had more control over my business than I did.
The worst part about all of this? I did not even realise this was a problem and most people don’t. They are delighted to get bigger clients, because this means more money. It also means bigger risk.
Client concentration is not just an operational concern. It is a valuation issue. It directly affects what your agency is worth.
Why Client Concentration Is Dangerous
The obvious risk is a single client leaving. But concentration creates problems even when the client stays.
Negotiating power shifts. When a client knows they represent 30% of your revenue, the dynamic changes. They may not exploit it deliberately, but the implicit power is there. You find yourself saying yes to scope changes you would normally push back on. You offer discounts to keep them happy. You prioritise their work over other clients because the stakes are higher. All of that erodes your margin over time.
Decision-making distortion. Every strategic decision gets filtered through the question: “Will this affect our biggest client?” Hiring decisions, pricing changes, service offerings. You stop running your agency and start running a satellite office for one company. I have seen this happen to agencies doing £1.5M where one client represented £500K. The tail wags the dog.
Buyer perception. If you are thinking about selling your agency, client concentration is one of the first things a buyer examines. Any buyer will apply a discount to a valuation where the top client represents more than 25% of revenue. Some buyers will walk away entirely above 40%. The logic is simple: they are not just buying your agency. They are buying the risk that your biggest client might leave after the deal.
How to Measure It
Before you can fix it, you need to know the numbers.
Pull your revenue data for the last 12 months. Break it down by client. Calculate what percentage each client represents of total revenue.
The benchmarks:
| Metric | Healthy | Watch | Danger |
|---|---|---|---|
| Largest client | Below 5% | 5-15% | Above 15% |
| Top 3 clients combined | Below 40% | 40-55% | Above 55% |
| Top 10 clients combined | Below 70% | 70-80% | Above 80% |
If your largest client is above 15%, you have a concentration problem. If your top 3 are above 55%, it is urgent.
Also look at the trend. Is concentration increasing or decreasing? An agency growing from £500K to £1M by adding one large client is actually becoming more fragile, even though revenue is up.
The Growth-First Approach
The instinct when you spot concentration risk is to think about reducing the big client. Putting limits on how much work you take from them. Maybe even firing them.
That is almost always the wrong approach.
Instead of shrinking your biggest client, grow everything else. The goal is not to reduce the top client’s revenue. It is to increase total revenue so that the top client’s percentage naturally decreases.
If your biggest client generates £15,000 a month and your total revenue is £45,000, they represent 33%. If you grow total revenue to £75,000 without growing that client, they drop to 20%. Same client. Same revenue from them. Completely different risk profile.
This is the approach that worked for me. I kept servicing the big client at the same level, but I redirected all business development effort toward new client acquisition and growing mid-tier accounts.
Five Practical Strategies
1. Set a New Business Target That Forces Diversification
If your top client is at 30% of revenue, set a target to sign 3 new clients worth at least £3,000/month combined within the next 90 days. Make that the number one priority for your sales effort.
Do not leave this as a vague goal. Put it in your pipeline. Track it weekly. If you are not making progress by week 4, you need to increase activity (more outreach, more proposals, more follow-ups) or lower the revenue threshold for new clients you will accept.
2. Grow Your Mid-Tier Clients
You almost certainly have clients paying £1,000 to £2,000 a month who could be paying £3,000 to £5,000. They are not paying more because nobody has asked.
Run an account review for every client in your middle tier. What else do they need that you could provide? What are they buying from other suppliers that you could handle? What problems are they talking about that you could solve?
One agency I worked with discovered that 4 of their mid-tier clients were spending £2,000 to £5,000 a month with a separate digital agency for paid media. They were already doing the creative work. Adding paid media management was a natural extension. Within 6 months, they had moved 3 of those clients from £1,500 to £4,500 a month. That alone shifted client concentration significantly.
3. Diversify Your Service Offering
If all your revenue comes from one type of work (say, brand identity), you are exposed to both client concentration and service concentration. Adding a complementary service (web design, content strategy, paid media management) gives you a second reason for existing clients to spend more and a new reason for prospects to choose you.
The key word is complementary. Do not add a service that has nothing to do with your core offering. The new service should be something your existing team can deliver or something you can staff with one additional hire.
4. Build a Retainer Base Across Many Clients
Retainers solve concentration in two ways. First, they create recurring revenue that is spread across multiple clients. Second, they reduce the likelihood of any client leaving suddenly because the relationship is ongoing rather than project-based.
If you currently have 3 retainer clients and 12 project clients, your next 6 months should focus on converting 4 to 6 of those project clients into retainer relationships. Even small retainers (£500 to £1,000/month) add up and reduce concentration when spread across enough clients.
5. Protect Yourself Contractually
For your largest clients, push for longer contract terms with reasonable notice periods. A 12-month contract with 90 days’ notice gives you time to react if the client decides to move on. A month-to-month arrangement with 30 days’ notice gives you nothing.
I learned this the hard way. My biggest client was on rolling monthly terms. Every month I renewed the relationship implicitly without any protection. When I eventually moved them to a 12-month agreement with 60 days’ notice, it did not change the commercial relationship at all. It just gave me a safety net.
The 12-Month Concentration Reduction Plan
Months 1 to 3: Measure and diagnose. Pull the numbers. Identify your mid-tier growth candidates. Set a new business target.
Months 4 to 6: Execute. Sign 2 to 3 new clients. Grow 3 to 4 mid-tier accounts. Introduce or extend retainer offerings.
Months 7 to 9: Review and adjust. Has the top client percentage dropped? If not, increase new business activity. If yes, maintain the pace.
Months 10 to 12: Embed the discipline. Client concentration should be a standing item in your monthly review. If any client creeps above 20%, you know to accelerate diversification.
The goal is not perfection. The goal is progress. Moving your top client from 35% to 22% over 12 months is a meaningful improvement. It makes the business more resilient, more valuable, and more enjoyable to run because you are not constantly worried about one phone call changing everything.
Further Reading
For the financial systems that support concentration management, read the agency KPIs article and the agency cash flow guide.
If you are preparing for exit and concentration is a concern, the due diligence guide explains exactly how buyers evaluate client risk.
Take the free Agency Valuation to see how your client concentration scores. It is one of the seven factors in the valuation, and for most agencies it is the one with the most room for improvement. Book a discovery call if you want to work through a concentration reduction plan for your specific situation.