The red flags that matter most when buying a business, ranked: revenue that is not repeatable (channel dependence, one-off spikes, aggressive recognition), adjusted EBITDA inflated by indefensible add-backs, any customer above 20% of revenue, a business that cannot run without its owner, a working capital hole, deferred maintenance capex, and unresolved litigation or compliance exposure. Most are price issues you can engineer around; misrepresented revenue, concentration above 35% and systemic non-compliance are the genuine walk-aways. After twelve years of closed transactions, our observation is blunt: buyers rarely lose money to dramatic fraud. They lose it to ordinary numbers quietly borrowed from the future. Here is how to catch each one early, before diligence costs get serious.
Is the revenue real, or borrowed from the future?
Revenue quality sits at the top of the list because everything else is priced off it. Three failure modes cover most cases.
Channel dependence. If more than 70% of revenue arrives through one platform, one Amazon account, one Meta ad account, one distributor relationship, you are buying a channel position, not a business. A single policy change or algorithm shift can remove the earnings you paid a multiple on. Ask for revenue by channel, monthly, for 36 months. Price at the bottom of the band or structure the deal heavily.
One-off spikes. Sellers come to market after their best twelve months, and trailing figures flatter a spike that is already fading. A viral quarter, a single large contract, a competitor's stock-out, none of it repeats. Monthly revenue over three years, repeat-purchase or renewal rates, and pipeline against closed business separate a trend from an event.
Aggressive recognition. Multi-year contracts recognised upfront, the channel stuffed in the final two quarters, returns spiking just after period end. Ask for the deferred revenue schedule and post-period credit notes. This one is different in kind: channel dependence is a price conversation, but recognition games tell you how the seller behaves when the numbers matter, and that usually makes it a walk-away.
How much of the adjusted EBITDA is fiction?
The price is a multiple of adjusted EBITDA, typically 3.5x to 9x for consumer and services businesses in the lower mid-market, so every indefensible add-back you accept costs you 3.5x to 9x its value at completion. The common fictions: "one-off" marketing that recurs every year, an owner salary replaced at half its market rate, and add-backs for staff whose work still has to be done by someone. The test for every line is the same: would this cost genuinely not exist under new ownership, and can the seller prove it? Rebuild EBITDA yourself from monthly management accounts rather than marking up the seller's bridge, our guide to which add-backs are defensible covers the standard categories. When total adjustments exceed roughly 30% of reported EBITDA, negotiate off your own rebuilt number. This is a price issue, until the seller keeps defending a fiction after seeing the evidence, at which point it is a character issue.
What happens when the biggest customer leaves?
Concentration is the easiest flag to measure and the most frequently rationalised away. Below 10% for the largest customer, price normally. From 10% to 20%, read the contracts: notice periods, change-of-control clauses, pricing review dates. Above 20%, structure protection, escrow, an earnout tied to retention, contract assignment as a completion condition. Above 35% without long-term contracted revenue, most experienced buyers in our buyer network either walk or restructure so the risk stays with the seller. Detection takes one schedule, revenue by customer for three years, which is why a seller's reluctance to produce it is itself the red flag. The same logic applies to supplier concentration: one manufacturer with no qualified alternative holds your margin in their hands.
Can the business run without the owner?
In founder-led businesses, most of the lower mid-market, the question is not whether the owner matters, but what exactly walks out of the door with them. Ask who owns the top five customer relationships, who sets prices, who approves hires, and when the founder last took two consecutive weeks fully offline. If every answer is the founder, you are buying a job with goodwill attached. This is usually a structure issue: a 6 to 12 month handover with 20% to 40% of the price deferred against transition milestones. It becomes a walk-away when the owner is the product, a personal brand, licences held personally, relationships that demonstrably will not transfer.
Working capital: the surprise that arrives after completion
Lower-mid-market deals are typically done cash-free, debt-free with a normal level of working capital, and "normal" is where buyers get hurt. In the final months before completion, sellers collect receivables hard, run stock down and stretch payables, the completion balance sheet looks lean, and the new owner funds the refill from their own cash. Set the peg off a 12-month monthly average, 24 months if the business is seasonal, and adjust pound for pound at completion. If the business is growing 30%+ in a stock-heavy category, model the cash that growth consumes on top. This is never a walk-away, it is simply the most frequently bungled price mechanic in first-time acquisitions.
Deferred capex: the profit that was never real
Trailing EBITDA looks excellent when the owner stopped investing two years ago. Compare capex to depreciation over five years: maintenance capex running persistently below 60% to 70% of depreciation means the profit you are paying a multiple on was partly funded by consuming the asset base. Walk the site, age the asset register, and check when core systems were last upgraded. This is a straight price issue: quantify the catch-up spend and deduct it from enterprise value pound for pound. Never pay a multiple on EBITDA the assets cannot sustain.
Litigation and compliance: the binary risks
The six flags above scale with severity; these are binary. The recurring ones in our deals: contractors who are really employees, VAT or sales tax uncollected across borders, IP developed by freelancers and never formally assigned, product compliance in regulated categories, and licences that do not transfer on a share sale. Run litigation searches, get tax position papers, and trace the IP assignment chain early. A quantifiable, one-off claim is handled with a specific indemnity or escrow, 10% to 20% of the price held back is common. Walk away when the exposure is systemic: if the margin only exists because the business does not comply, you are not buying profit, you are buying the liability.
Which red flags are price issues, and which are walk-aways?
The thresholds we apply when we value acquisition targets:
- Customer concentration. Largest customer under 10%: price normally. 10% to 20%: contract diligence. 20% to 35%: structure with escrow or a retention earnout. Over 35%: walk, or the seller keeps the risk.
- Channel dependence. One platform over 70% of revenue: bottom of the band, for consumer brands that means pricing towards 3.5x rather than 9x EBITDA.
- Add-back ratio. Adjustments above 30% of reported EBITDA: rebuild the number yourself and negotiate off it.
- Owner dependence. Fails the two-week absence test: defer 20% to 40% of price against a 6 to 12 month handover.
- Maintenance capex. Persistently below 60% to 70% of depreciation: deduct the catch-up spend from enterprise value, £ for £.
- Working capital. Peg off a 12-month monthly average (24 for seasonal businesses), adjusted pound for pound at completion.
- Walk-away triggers. Misrepresented or aggressively recognised revenue, concentration over 35% with no contracts, systemic non-compliance, and a seller who defends a fiction after seeing the evidence.
What to do next
Run these checks against a live target before you spend heavily on advisers, most of the data sits in monthly management accounts any serious seller can produce inside a week. Test the price against real transactions with our free comparable transactions tool, review current mandates on our active deals page, or talk to us about buy-side support.
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Get your free valuation ↗Frequently asked questions
What are the biggest red flags when buying a business?
Ranked by how often they cost buyers money: revenue that is not repeatable (one dominant channel, one-off spikes, aggressive recognition), inflated adjusted EBITDA, any customer above 20% of revenue, owner dependence, working capital holes, deferred capex and unresolved litigation or compliance exposure. The first two do the most damage because price is a multiple of earnings, at typical lower-mid-market multiples of 3.5x to 9x, every fictional unit of EBITDA is overpaid many times over.
How much customer concentration is too much when buying a business?
Under 10% for the largest customer is comfortable. Between 10% and 20%, review contracts for notice periods and change-of-control clauses. Above 20%, structure protection into the deal, escrow, an earnout tied to retention, or contract assignment as a completion condition. Above 35% without long-term contracted revenue, most experienced buyers either walk away or restructure the deal so the concentration risk stays with the seller.
How do I know if adjusted EBITDA is inflated?
Rebuild it yourself from monthly management accounts instead of marking up the seller's bridge, then test every add-back against one question: would this cost genuinely not exist under new ownership, and can the seller prove it? Treat total adjustments above roughly 30% of reported EBITDA as a signal to negotiate off your own number. The commonest fictions are recurring 'one-off' marketing, under-replaced owner salaries and add-backs for staff whose work still has to be done.
Is owner dependence a reason not to buy a business?
Usually no, it is a structure issue. A 6 to 12 month handover with 20% to 40% of the price deferred against transition milestones covers most cases. It becomes a walk-away when the owner is the product: a personal brand, licences held personally, or customer relationships that demonstrably will not transfer. A quick test: ask when the owner last took two consecutive weeks fully offline.
What working capital should be left in a business when you buy it?
A normal operating level, defined as a peg based on a 12-month monthly average, 24 months for seasonal businesses, and adjusted pound for pound at completion. Never accept the completion-date snapshot alone: sellers routinely collect receivables hard, run down stock and stretch payables in the final months, leaving the new owner to fund the refill from their own cash.
Should I walk away from a business with pending litigation?
Not automatically. A quantifiable, one-off claim can be handled with a specific indemnity or an escrow, holding back 10% to 20% of the price is common. Walk away when the exposure is systemic or unquantifiable: misclassified contractors, uncollected VAT or sales tax across borders, or a margin that only exists because the business does not comply. In those cases you are buying the liability, not the profit.