The 60% Problem: What One Anchor Client Really Costs a Seven-Figure UK Firm

You know the moment. You’re scrolling the spreadsheet at half nine at night and the top line says £1.4m, and £860k of it has the same logo next to it. That’s not a sales win any more. That’s a dependency, and it’s sitting on your balance sheet wearing a nice suit.

Customer concentration is the quiet tax on fast growth. Nobody plans it — you plan a product, a price, a first hire. But the anchor client arrives, pays on time, asks for more, and suddenly you’ve built a seven-figure business with a single point of failure. The good news: you don’t have to fire them. You just have to make them optional.

When one logo quietly becomes the payroll

A founder in the Midlands we spoke to runs a £2.1m design-and-build outfit. One housebuilder accounts for 58% of revenue and, more painfully, roughly 90% of the work that keeps four site teams busy between November and February. When that client pushed payment terms from 30 days to 60 last winter, the firm burned through three months of cash in six weeks. Nothing had gone wrong commercially. The business was simply built on a single tap.

That’s the pattern. Concentrated revenue doesn’t feel risky while the relationship is warm. It feels like focus. It feels like the thing every business book tells you to do — go deep with your best customer. The risk only shows up when something external shifts: a change of procurement lead, a merger, a budget freeze, a new CFO with a spreadsheet and a mandate.

The number a lender or buyer actually marks you down for

Here’s what most founders don’t find out until too late. Concentration isn’t just an operational worry — it’s priced in.

Lenders will often cap how much of an invoice finance facility can sit with one debtor, sometimes as low as 20–25%. Covenant negotiations get awkward when a single client can trigger a breach by paying a fortnight late. And on the equity side, a buyer looking at a £2m EBITDA business where one customer is 55% of revenue will typically apply a discount of one to two turns of EBITDA — or push hard for deferred consideration, an earn-out and a chunk held in escrow for 24 months.

Then there’s the clause nobody reads until diligence: change of control. Plenty of large-client contracts allow termination if your business is sold. So the very buyer you’re courting can lose the deal the moment your anchor client exercises a right you signed in 2021 without blinking.

Fix the cash before you fix the sales

The fastest de-risking lever isn’t a new client. It’s the invoice.

• Stagger your billing dates. If everything lands in one week, one late payer empties the account.
• Charge deposits on project work. 30% up front, milestones through the build, final 10% on sign-off. It’s normal in construction, normal in agency land, and increasingly normal everywhere else.
• Move from big lumpy invoices to monthly retainers wherever you can. Same annual value, far smoother cash.
• Hold three months of fixed costs in a separate account. Not as an emergency fund — as a confidence fund, so you never negotiate from panic.
• Look at credit insurance or a letter of credit if a single debtor is over 40% of revenue. It costs a fraction of a percent and buys real sleep.

Contracts: the four clauses that decide your fate

Get a proper commercial solicitor to read your anchor contract once. A few thousand pounds now is cheaper than a wobble later.

1. Notice period. Thirty days’ notice on 60% of revenue is not a contract, it’s a hope. Push for 6–12 months, or a fee in lieu.
2. Termination for convenience. If they can walk for any reason with a month’s notice, you have no floor under the business.
3. Change of control. Either delete it, or get pre-agreed consent language so a sale doesn’t trigger an exit door.
4. Price escalation. Link fees to CPI or an agreed index. Fixed pricing over a five-year term is a slow-motion margin cut.

While you’re in there, check exclusivity (are you barred from selling to competitors?) and benchmarking clauses. Both can quietly strangle a second revenue engine before it starts.

Building engine two without torching engine one

The mistake founders make is treating diversification as a rebrand. It isn’t. It’s a small, boring, repeatable experiment that runs alongside the day job.

The playbook that works: take the exact thing you already sell to your anchor client and sell it to three or four smaller buyers in a neighbouring sector. Same product, same delivery, different logo. Give it one day a week of founder time and a target — say, 15% of revenue from non-anchor clients within twelve months, no single client above 30% within three years.

Ask your anchor client for a reference. Most will say yes, and a case study with a recognisable name shortens every future sales cycle. Track concentration monthly on a single dashboard line: top client as a percentage of revenue. When it trends below 40%, your business has fundamentally changed shape.

Keep the anchor close while you widen the base

Diversifying doesn’t mean distancing. Multi-thread the relationship — know at least three people in that organisation, not just your champion. Run quarterly business reviews with data that shows the money you make or save them. Become administratively awkward to remove.

And say it out loud. “We’re growing our client base over the next two years — here’s the plan, and here’s what stays the same for you.” Most clients respect the honesty. Some will actively help, because a supplier with a broader base is a supplier that survives.

Your 90-day de-risking sprint

Weeks 1–2: concentration audit. Revenue by client, gross margin by client, cash at risk if each one stopped paying tomorrow.

Weeks 3–4: contract review. Identify the four clauses above and price the cost of renegotiating at renewal.

Weeks 5–6: terms reset. Deposits, milestones, staggered invoicing, three-month buffer.

Weeks 7–10: engine two. Pick your adjacent sector, build the case study, book ten conversations.

Weeks 11–13: talk to your lender with clean numbers and a plan. A bank that sees you actively reducing concentration lends differently.

The anchor client got you here. Nobody’s suggesting you ungrateful your way out of seven figures. But a business that can survive losing its biggest customer is worth measurably more than one that can’t — to a buyer, to a lender, and to you at half nine on a Tuesday night.