Author byline suggestion: Adeel Bashir, Solicitor and Founder, Nouveau Legal. Nouveau Legal is a commercial law practice in Middlesbrough advising UK startups, SMEs and corporates on acquisitions, contracts, employment and intellectual property.

Last reviewed: September 2026

Short answer

Legal due diligence is the investigation a buyer carries out before completing a business purchase, to confirm that the seller owns what they are selling, that the contracts and people supporting the revenue will survive the sale, and that no hidden liability transfers with the deal. On a typical UK SME acquisition it takes two to six weeks, sits between heads of terms and exchange, and covers seven areas: corporate ownership, contracts, employees, property, intellectual property, disputes and regulatory compliance, and tax. What you find does not just inform whether to buy. It determines the price, the warranties, the indemnities and the retention you negotiate in the purchase agreement.

What is legal due diligence when buying a business?

Due diligence is the structured investigation of a target business before you commit to buying it. Financial due diligence, usually run by your accountant, tests whether the numbers are real. Commercial due diligence tests whether the market and the customer base are real. Legal due diligence tests whether the business can actually be transferred to you, intact, without dragging someone else’s problems across with it.

The process is buyer-led. You issue a due diligence questionnaire, the seller populates a data room, and your solicitor works through the disclosures raising follow-up enquiries. In English law the governing principle is caveat emptor, buyer beware. The seller is under no general duty to volunteer bad news. If you do not ask, and the contract does not contain a warranty covering the point, you usually have no remedy after completion. That single principle is why due diligence is not an administrative formality.

How long does due diligence take, and what does it cost?

For an SME deal in the £250,000 to £5 million range, allow two to six weeks from the point the data room opens, assuming the seller is organised. Deals slip when the seller is a small owner-managed company with informal record keeping, which is common: no signed customer contracts, a lease that was never formally assigned, a website built by a freelancer with no IP assignment.

Legal fees for due diligence and the purchase documents on an SME acquisition commonly run from around £4,000 to £20,000 plus VAT depending on complexity, structure and how clean the target is. Fixed-fee scoping is possible once your solicitor has seen the heads of terms. For a fuller breakdown of how commercial legal costs are structured, see our guide to what a commercial solicitor costs in the UK.

Share purchase or asset purchase: why deal structure changes everything

Before the checklist, settle the structure. It dictates what you are actually buying and therefore what you need to investigate.

	Share purchase	Asset purchase
What you buy	The company itself, including every liability it has ever incurred	Selected assets and contracts only
Liabilities	All historic liabilities come with the company, known and unknown	Stay with the seller, except employees under TUPE
Due diligence depth	Deeper. You inherit the past, so you investigate the past	Narrower but still substantial, focused on title to the assets
Contracts	Usually continue automatically, unless a change of control clause bites	Must be novated or assigned individually, third party consent often needed
Employees	Stay with the company, no transfer event	Transfer automatically under TUPE
Property	Lease stays with the company, landlord consent may still be required on change of control	Lease must be assigned, landlord consent almost always required
Tax on the transfer	Stamp duty at 0.5% on the consideration for the shares	SDLT on any land, currently 0% to £150,000, 2% to £250,000, 5% above
Typically favours	Seller	Buyer

A point of timeliness for 2026: HMRC published a policy paper in July 2026 proposing a Securities Transfer Tax to replace stamp duty and stamp duty reserve tax with a single self-assessed 0.5% charge administered through an online portal, and confirming an intention to remove the current £1,000 exemption threshold. Small share transfers that fall outside the charge today may not in future. If your deal involves a staged share transfer over several years, factor this in now.

The 2026 legal due diligence checklist

1. Corporate ownership and constitution

Confirm the seller can actually sell. Check the register of members against the share certificates and the Companies House filing history, not just the seller’s word. Look for unissued or partly paid shares, options, convertible loan notes and pre-emption rights in the articles that could block a transfer. Review any shareholders’ agreement for drag-along and tag-along provisions.

There is a 2026 wrinkle here. Identity verification at Companies House became mandatory for new director appointments and PSC registrations from 18 November 2025 under the Economic Crime and Corporate Transparency Act 2023, with in-post directors and existing PSCs phased in through their next confirmation statement. If the target has not completed verification, the company can find itself unable to make further filings, which is an awkward discovery the week before completion. Ask for verification status in your first enquiry list. Our guide to company law compliance in the UK sets out the wider director obligations you will inherit.

2. Contracts and change of control

Read the contracts that produce the revenue you are paying for. In practice, three things matter more than the rest:

Change of control clauses. Many customer and supplier agreements give the counterparty a right to terminate on a change of ownership. On a share purchase this is the single most common way a buyer loses the value they thought they bought.
Concentration risk. If 40% of turnover sits with one customer on a 30-day rolling term, you are not buying a contracted revenue stream. You are buying a relationship.
Onerous terms. Uncapped liability, unlimited indemnities, long exclusivity, auto-renewal and one-sided termination rights all travel with the business. Our post on spotting hidden risks in supplier contracts covers the clauses that cause the most damage after completion.

Also check what is not written down. Unsigned terms, purchase orders referencing superseded conditions and long-standing arrangements held together by habit are all common in owner-managed businesses, and all become your problem on day one.

3. Employees and TUPE

On an asset purchase, employees assigned to the transferring business move to you automatically under the Transfer of Undertakings (Protection of Employment) Regulations 2006. You cannot cherry pick, and dismissals for a reason connected to the transfer are automatically unfair unless there is an economic, technical or organisational reason entailing changes in the workforce.

The seller must provide employee liability information under regulation 11 at least 28 days before the transfer, covering identities, ages, terms, and disciplinary, grievance and claims history from the previous two years. Failure to provide it, or providing it inaccurately, gives you a tribunal claim. Treat the 28-day point as a diary deadline, not a nicety.

The 2026 reason to take this seriously is the Employment Rights Act 2025. From 1 January 2027 the qualifying period for ordinary unfair dismissal drops to six months and the cap on the compensatory award, currently the lower of 52 weeks’ pay or £118,223, is removed. Employees already in post benefit immediately. A workforce you inherit in late 2026 will have materially stronger protection within weeks of completion, so restructuring plans that assumed the old two-year qualifying period need rethinking before you sign. If post-completion headcount reduction is part of your model, read our step-by-step redundancy process guide for employers before you commit to the numbers.

Check contracts of employment too. Missing written particulars, unenforceable restrictive covenants and undocumented bonus schemes are all standard findings. See what employers must include in an employment contract.

4. Property and premises

Obtain the lease, the licence for alterations, the rent deposit deed and the last three years of service charge accounts. Look for the break clause and its conditions, the rent review pattern, repairing obligations and any alienation restrictions. On an asset purchase, landlord consent to assign is almost always required and routinely becomes the critical path item that delays completion. Start it early. Also check whether the seller’s personal guarantee is being released or whether the landlord will expect one from you.

5. Intellectual property and data

Ask one blunt question: who legally owns the brand, the software, the designs and the website? The answer is frequently not the company. Founders register trade marks personally. Freelance developers retain copyright by default under UK law unless there is a written assignment. Logos created by an agency belong to the agency until assigned. If the IP does not sit in the entity you are buying, it does not transfer, and no amount of goodwill fixes that after completion.

Check registered rights at the UK IPO for ownership, renewal dates and classes. Check domain registrations and social handles, which are often in a personal account. Then check data: a UK GDPR compliant privacy notice, a lawful basis for the marketing database you are valuing, and processor agreements with suppliers. Our guide to protecting intellectual property in the UK explains how to put this right where the target has not.

6. Disputes, regulatory matters and compliance

Request details of live, threatened and recently settled disputes, together with the correspondence. On a share purchase these come with the company. Check licences and authorisations required for the sector, health and safety records, insurance history including claims, and any correspondence with a regulator or with HMRC. Ask specifically about matters that have not yet crystallised into a claim, because those are the ones a seller is least likely to volunteer.

7. Tax and financial liabilities

Your accountant leads here, but the legal side matters: outstanding charges at Companies House, debentures, personal guarantees, director loan accounts, deferred consideration owed to previous owners, and VAT or PAYE arrears. On a share purchase a tax covenant in the purchase agreement is standard and should be negotiated rather than accepted in the seller’s draft form.

What happens when due diligence finds a problem?

Findings do not usually kill a deal. They move price and risk. There are five standard responses, and choosing the right one is where an experienced acquisition solicitor earns their fee:

Price reduction. Appropriate for a quantifiable, certain liability, for example an underpaid holiday pay entitlement.
Specific indemnity. The seller agrees to reimburse you pound for pound if a defined risk materialises, for example a known tribunal claim. Unlike a warranty claim, you do not need to prove loss of value to the business.
Condition precedent. Completion happens only once the issue is fixed, for example the IP is assigned into the company or landlord consent is obtained.
Retention or deferred consideration. Part of the price is held back for a defined period against identified risks.
Walk away. Rare, but the right answer where the target’s core revenue rests on contracts that terminate on change of control and the customers will not confirm they intend to stay.

Warranties and the disclosure letter: how findings reach the contract

Warranties are statements of fact by the seller about the business. If a warranty turns out to be untrue and you suffer loss, you have a contractual claim. The seller answers with a disclosure letter, which qualifies the warranties by disclosing exceptions. Anything properly disclosed cannot later be claimed on.

This is why due diligence and the drafting stage are one process, not two. A finding you spotted but did not convert into a warranty, an indemnity or a price adjustment is a risk you have simply agreed to accept. Read the disclosure letter with the same care as the purchase agreement, and resist general disclosure of the entire data room, which effectively neutralises the warranties you negotiated.

Three mistakes we see UK buyers make

Starting due diligence after the heads of terms are signed and exclusivity has expired. Exclusivity periods are typically 8 to 12 weeks. If you spend four of them waiting for a data room, you lose your negotiating position at exactly the point you need it.

Relying on the accountant alone. Financial due diligence will not tell you that the key customer contract terminates on change of control, that the trade mark is registered to the founder personally, or that three employees have live grievances.

Treating warranties as a substitute for investigation. A warranty is only as good as the seller’s ability to pay a claim two years after they have spent the proceeds. Investigate first, warrant second.

Frequently asked questions

What is legal due diligence when buying a business? It is the investigation a buyer’s solicitor carries out into a target business before completion, covering corporate ownership, contracts, employees, property, intellectual property, disputes, regulatory compliance and tax, to identify risks that would transfer with the purchase.

How long does due diligence take when buying a UK business? Typically two to six weeks for an SME acquisition once the data room opens. Poor record keeping, landlord consent to assign a lease and third party consents to novate contracts are the three most common causes of delay.

Do I need a solicitor to carry out due diligence? There is no legal requirement, but the English law principle of caveat emptor means a buyer generally has no remedy for problems they failed to discover and did not cover by warranty or indemnity. See our guide to whether you need a business purchase solicitor.

What is the difference between a warranty and an indemnity? A warranty is a statement of fact; if it is untrue you must prove the resulting loss in value to recover. An indemnity is a promise to reimburse a specific defined liability pound for pound, without needing to prove diminution in value.

Does due diligence differ for a share purchase and an asset purchase? Yes. A share purchase means inheriting every liability the company has, so investigation goes deeper and further back. An asset purchase is narrower, focusing on title to the assets being transferred, third party consents and TUPE obligations for employees.

What happens to employees when I buy a business? On a share purchase they stay with the company and nothing changes. On an asset purchase they transfer automatically under TUPE, with their existing terms and continuous service preserved, and the seller must supply employee liability information at least 28 days before the transfer.

What does due diligence cost? On an SME acquisition, legal fees for due diligence and the transaction documents commonly range from around £4,000 to £20,000 plus VAT depending on deal size, structure and how well documented the target is.

Thinking of buying a business?

Nouveau Legal advises UK buyers on acquisitions from first heads of terms through due diligence to completion, on fixed fees agreed in advance and in plain English. We work across business structure and acquisitions, customer and supplier contracts, employment and HR, intellectual property and company law compliance.

Book your free call and we will scope the due diligence exercise and give you a fixed quote before any work starts.

This article is general information about English and Welsh law as at September 2026 and is not legal advice for your specific transaction.

Legal Due Diligence When Buying a Business in the UK: The 2026 Checklist