The fastest way for a good deal to turn sour is hidden concentration risk. You buy the numbers you see, but you live with the relationships behind those numbers. In London, that theme runs through everything from neighbourhood service firms to specialist manufacturers tucked inside industrial estates. The names on a revenue report, and the dependencies buried in a purchasing ledger, will tell you whether your new business stands on a wide base or a single leg.
Concentration risk sounds technical, but it is simply this: too much of your fate rests with too few counterparties. On the supply side, one or two vendors hold the keys to your stock, your costs, or a proprietary component. On the customer side, a small cluster of buyers, sometimes just one, makes up the bulk of your revenue. If any one of those players sneezes, your P&L catches a cold.
Two Londons, one lesson
I have worked with buyers on both sides of the Atlantic who type the same searches into their browser at night, coffee in hand: business for sale in London, buy a business in London, off market business for sale. Some are combing through companies for sale London and meeting owners in Bermondsey. Others are across the pond walking shop floors in London, Ontario, asking a foreman which US suppliers ship on time.
Different cities, different accents, same core questions. In London, UK, the supply chain can run through EU distributors, specialized wholesalers in Park Royal, or exclusivity tied to a European OEM. Customers may sit inside a TfL framework agreement or on the roster of a handful of blue-chip property managers. In London, Ontario, suppliers often run through the 401 corridor and the US Midwest. Customer concentration can mean two US automotive customers or a regional health system across the border. Currency, customs, and transport time change the texture, but the underlying exposure is the same.
Whether you are speaking with local advisors, big platforms, or niche firms like Liquid Sunset Business Brokers or Sunset Business Brokers, the sourcing channel does not change the work. You still have to unpack who really controls price, volume, and delivery.
What concentration actually looks like, in numbers you can use
There is no single magic number, but there are patterns that consistently separate durable businesses from brittle ones.
- Revenue concentration: Add up the revenue by customer, ranked from largest to smallest. If the top customer is more than 25 to 30 percent, your eyebrows should rise. Over 50 percent means you are buying a key account more than a business. Look at the top five. If they exceed 60 to 70 percent combined, you face concentration even if no single customer looks extreme. Supplier reliance: On the supply side, focus less on spend share and more on switchability. A supplier with 40 percent of your spend who sells a commodity available from three other wholesalers is different from a supplier with 20 percent who holds the only tooling for a critical subassembly. Tenure and churn: Long relationships are not always safer. If the top customer has stayed for ten years but on non-binding purchase orders, you still have risk. If the supplier has supplied you for five years but just got acquired by a private equity roll-up, expect pricing and terms to move. Terms and protections: Indexation to input costs, rebates, growth discounts, and step-down clauses in contracts can move gross margin by three to five points during a bad quarter. Payment terms determine working capital stress if a large buyer stretches you to 60 or 90 days. Geographic spread: In London, UK, a supplier base concentrated in the EU now carries customs, VAT, and transport volatility. In London, Ontario, a customer base concentrated in the US carries currency risk and border delays. Both affect concentration because they compound a single relationship with macro friction.
If you want one quantitative lens, the Herfindahl-Hirschman Index can be useful. Square each customer’s revenue share and sum them. An HHI above 1,800 points to high concentration. Treat it as a guide, not gospel. HHI does not capture lock-in, substitute availability, or the optionality of your brand.
The story behind the ledger: supplier concentration in practice
A few examples from deals I have seen will help the numbers breathe.
A specialist flooring distributor in North London had 70 percent of its revenue tied to three European brands. One brand controlled a signature product line with colours and finishes competitors could not match. Contracts were “evergreen” but cancellable with six months’ notice. The distributor’s margin hinged on a 9 percent year-end rebate. When the manufacturer changed ownership, the rebate shifted to a tiered structure tied to growth rather than volume. Gross margin dropped by two points. The buyer who understood that the rebate was equivalent to the difference between a 12 percent and 14 percent EBITDA margin had a clear view of the landmine.
In London, Ontario, a precision machine shop carved parts for a US Tier 1 supplier. The supplier owned the tooling and stored it at the shop. That meant the work could move in a week. The owner believed “they would never leave, not after 15 years.” Then the Tier 1 won a new platform with different materials and tolerances. Work stayed for a year, then halved. The shop was not weak in capability, it was weak in negotiating leverage because the tooling did not belong to them.
The pattern repeats across sectors. The risk is often not visible in the accounting system. It lives in who owns the mold, who holds the drawing, who has the listing on the retail shelf, and which brand your website is allowed to show.
Customer concentration, and why stability can be a trap
A five year revenue chart with a flat top line from a single customer feels stable. It is usually a ceiling. When a facilities services firm in West London touted a 15 year relationship with a property management company, the headline looked great. The detail did not. The master services agreement had an annual retender provision with a right of first refusal. The client used that clause every two years to take 3 percent off rates. The supplier responded by stretching shifts and sweating overtime. EBITDA never grew. The relationship was stable, but the economics bled slowly.
On the other hand, I have seen concentrated revenue that was healthy. A lab testing business had 40 percent with an NHS trust on a framework with guaranteed minimum volumes and CPI indexation. Renewal involved quality metrics, not price alone. Pipeline reports showed multiple new tender opportunities. Concentration existed, but the counterparty’s procurement rules and the contract’s structure softened the risk.
When you assess customer concentration, test three things: assignability on change of control, how price is set, and the switching cost your service imposes. Assignability tells you whether your deal triggers a renegotiation at the worst possible time. Price mechanics tell you how a recession or wage spike will hit margins. Switching cost tells you whether your customer walks for a 2 percent discount or sticks because your work is embedded in their process.
The contracts matter more than the CRM
Spend your diligence energy on contract terms, not only on logos and volumes. I look for the following items, and I prefer to read the actual documents rather than summaries. Change of control clauses that void or trigger termination rights can turn a signed LOI into a scramble for consents. Term and termination language, especially convenience termination, will show you who has the optionality. Price adjustment provisions and indexation clauses either stabilize margins or push volatility into your lap. Non-exclusivity and territory provisions tell you whether you can grow beyond current boundaries. Rebate and growth targets are often where real margin hides. Service levels and liquidated damages clauses reveal downside in operational hiccups.
Assignability is a frequent gotcha. Many UK and Canadian customer contracts are silent on assignment, which defaults to common law rules. Others require express written consent. For supplier contracts, watch for volume commitments and take-or-pay language, which can bite in a downturn.
Price power, indexation, and the quiet squeeze
Small businesses do not lose all at once. They give away two points here and one point there. Over a few years, a concentrated customer pushes for early payment discounts, then lengthens terms for their own cash cycle, then asks for a rebate tied to “partnership.” If your costs are not indexed, you finance the partnership. With concentrated suppliers, the squeeze can come through freight surcharges, currency pass-throughs, and minimum order quantities that bloat working capital.
In the UK, energy and transport costs have been volatile. If your suppliers indexed to energy while your customer prices remained fixed for a year, you had a trap baked into your income statement. In Ontario, currency swings against the US dollar can change cost of goods by high single digits. Some firms hedge, many do not. Contracts that treat foreign exchange and energy as pass-throughs can protect you, but they have to be read and enforced.
Logistics and operational choke points
Concentration is not only legal; it is operational. A bakery with one night driver who knows all route shortcuts has more concentration risk than its supplier ledger suggests. The same is true in manufacturing with one CNC programmer who holds all the macros, or in e-commerce where 80 percent of your revenue depends on one marketplace listing.
If the sole supplier sits in a region prone to strikes or port delays, that risk is not abstract. When Felixstowe slowed down, businesses with one freight forwarder had a bad month. Others who held relationships with multiple consolidators, or who could shift to Southampton or rail, absorbed the shock. In Ontario, winter storms and cross-border inspections have the same practical effect. When one snow day drops revenue by 50 percent because two major customers shut their doors, you are living with concentration whether or not your revenue report shows it.
Lenders, valuation, and how the market prices risk
Banks and private lenders in both Londons have a simple view. If your top customer is above roughly 30 percent, they will ask for longer amortization, stronger covenants, or a personal guarantee. If your top supplier is sole-source, they will ask for letters from the supplier or growth plans that reduce reliance. Lenders have seen what happens when a blue-chip buyer changes procurement policy or when a supplier gets bought. They will not let you borrow against hope.
Valuation follows the same logic. A 5 to 6 times EBITDA multiple for a diversified service firm can drop to 3.5 to 4.5 times if the top customer is too large or the main supplier owns the molds. If you can show a path to dilute the concentration within 12 to 18 months, smart sellers and buyers sometimes bridge that gap with earnouts or escrows tied to customer retention.
Due diligence that reaches beyond the spreadsheet
Concentration risk yields to fieldwork. You cannot desk-analyse your way out of it. The best diligence plans combine data pulls with conversations.
Start with twelve to thirty six months of sales by customer, margin by customer, and lost customer lists with reasons. If the system cannot produce margin by customer, ask for raw invoice and https://martinkffr749.cavandoragh.org/companies-for-sale-london-cybersecurity-risks-to-evaluate cost data to reconstruct it. Look at the shape of orders. One customer who buys a little every week is safer than one who buys once a quarter, even if annual spend is the same.
On the supply side, request a list of all suppliers with spend, their product categories, and any volume or rebate structures. Sit down with the operations lead and ask which purchase orders get flagged, who they call when a delivery is late, and which part numbers trigger a line stoppage. If a name appears three times in that conversation, that is a concentration point.
Meet the counterparties if you can. For customers, even a brief call to confirm satisfaction, understand renewal triggers, and test appetite for growth will tell you more than a glossy deck. Some corporates will not speak until post close. In that case, seek letters of comfort or run scenarios that assume partial loss. For sole-source suppliers, ask about capacity, lead times, and what happens if your order doubles. Their answer becomes your growth plan or your risk memo.
Practical ways to reduce concentration, starting on day zero
Here is a short, workable playbook I have used with buyers who inherit concentration and want to move it in the right direction.
- Map and rank exposure: Create a simple two by two grid, impact on the business and switchability. High impact, low switchability items become your top three priorities. Lock what you can: Convert handshake terms into written amendments, add indexation or price review windows, and clarify assignability post close. Build a second source: For critical SKUs, qualify an alternate and place a small but regular order to keep the relationship real. Tilt sales toward diversification: Incentivize your team on gross margin from new logos or from underrepresented sectors, not just total revenue. Invest in stickiness: For top customers, embed reporting, training, or light integration that raises switching cost without raising your fixed cost base.
Red flags worth slowing the deal for
If you see any of these, pause and reframe the price or the structure until you are paid for the risk.
- Change-of-control clauses that require consent from your top customer or sole supplier, with no fallback language. Supplier-owned tooling or brand usage rights that can be pulled on 30 to 90 days’ notice. A customer that accounts for more than 40 percent of revenue on a non-binding purchase order basis, with no service-level commitment. Rebates that make up more than half of gross margin improvement, especially if tied to year-over-year growth instead of absolute volume. A history of price concessions every twelve to twenty four months with no documented offset in scope or service levels.
When concentration is not a bug
The flip side is worth acknowledging. Concentration can be a moat when it sits on top of proprietary capability or regulated process. A contract electronics manufacturer that builds safety-critical assemblies under a customer’s quality system can enjoy decade-long runs with limited price pressure if it meets metrics. A software firm with deep integrations into a hospital’s scheduling and billing systems creates real switching friction. A supplier who won the only UK distribution rights to a niche European brand with loyal trade customers can hold pricing power, provided the brand’s owner is stable and aligned.
If you buy one of these, plan for life-cycle management rather than diversification for its own sake. You are in the relationship business, and your job is to deepen the sticky parts and formalize the economics so that margin is protected.
London specifics you should not ignore
In London, UK, supplier concentration often crosses borders. Watch for incoterms, duty treatment, and VAT flow in contracts. Currency clauses that reference specific FX bands can save a quarter. For customers in transport, construction, and public services, familiarize yourself with frameworks and mini-competitions that govern awards. A healthy share with one housing association can be low risk if the framework runs for years with renewal hurdles based on KPIs rather than headline price.
In London, Ontario, be ready for cross-border realities. US customers that represent a third of your revenue may pay in dollars on 60 day terms, while your Canadian suppliers need payment in 30 days. That mismatch becomes a working capital strain, not just a P&L item. Investigate credit insurance, forward contracts, and multi-currency accounts early. If your sole supplier sits in the US, confirm export control compliance and any state-level restrictions that might bite during trade spats.
Brokers, sourcing, and keeping your head straight
However you source, whether through big marketplaces, local advisors, or niche outfits, the diligence on concentration is your responsibility. Listings that say small business for sale London or companies for sale London, and their Canadian cousins like businesses for sale London Ontario and business broker London Ontario, vary in quality. Some sellers highlight key accounts as a badge of honour. It is your job to translate that pride into a risk-adjusted plan. Even if you find an off market business for sale through a quiet introduction, or you speak with business brokers London Ontario about a manufacturing target, your first filter remains the same: who can say no to you, and how many people can say it.
If you collaborate with a specific broker, ask them for cohort data. A good broker has seen what happens to similar businesses in their market and can tell you, for example, whether a 35 percent NHS exposure is common in diagnostics, or whether two US OEMs making up half the revenue is typical for a given machining niche. Use that to calibrate your price and your transition plan, not to skip diligence.
The first hundred days after closing
The day you own the business, the counterparty relationships become your job, not the seller’s. Be proactive. Call your top customers and suppliers in week one. Your tone matters. Do not ask for changes in month one. Ask for a meeting, listen, and confirm continuity. Then, in month two or three, begin to formalize what you can. If you inherited verbal discounts, turn them into written schedules with clear expiries. If you rely on rebate cheques, set calendar reminders for milestone checks and quarterly reconciliations.
Invest time in your team’s quiet experts. The warehouse lead who knows how to nudge a late pallet from a carrier, or the scheduler who can fill a deadhead truck, often controls as much risk as a contract clause. If one person holds a critical relationship, introduce a second. That is not politics, it is prudence.
When to walk, when to reprice, when to lean in
Walking away makes sense when concentration combines with fragility you cannot influence. A single buyer on non-binding terms with a stated plan to retender in six months is a coin flip. Do not bet the farm.
Repricing makes sense when the risk is real but manageable. If the top supplier owns the tooling, you can price in a year of diversification work and fund a new tool through an earnout that depends on retaining margin. If the top customer represents 35 percent but you have line of sight to three meaningful prospects, adjust the multiple and carry a contingency in your cash plan.
Leaning in makes sense when concentration is bound to a defensible franchise. If the customer’s process embeds your work and the contract indexes costs sensibly, your job is to keep service high and expand wallet share, not to dilute a great relationship out of fear.
Pulling it together
Buying a business in London, whether you mean Camden or the Forks of the Thames, is about reading people, contracts, and systems as much as it is about financials. Supplier and customer concentration risks are not reasons to panic, they are reasons to be deliberate. You do not need exotic analytics. You need clean customer and supplier lists, the patience to read real contracts, and the curiosity to ask who picks up the phone when things go wrong.
If you keep your head on those basics, you can buy a concentrated business at the right price, set the first hundred days to shore up the base, and grow from there. If you skip them because the seller is charming or the logo list looks impressive, you will find yourself negotiating price with a counterparty you do not control. That is the kind of concentration you want to leave for your competition.