Due Diligence: What to Expect When Selling Your Business

Due diligence is the comprehensive investigation a buyer conducts before completing a business acquisition. It is the process through which a prospective purchaser verifies the claims made about a business, identifies risks, and confirms that the transaction represents fair value. For sellers, understanding what due diligence involves — and preparing for it thoroughly — is one of the most important steps in achieving a successful sale.

In the UK mid-market, due diligence typically begins once heads of terms have been agreed and the business is taken off the market. It is a critical phase: deals that collapse most often do so during due diligence, usually because of issues that could have been anticipated and addressed in advance.

At its core, due diligence serves three purposes for the buyer:

• Confirming that the business is what it has been represented to be
• Identifying risks that may affect the price, deal structure, or decision to proceed
• Gathering information needed to plan the post-acquisition integration

For sellers, the due diligence period can feel intrusive and time-consuming. However, businesses that are well-prepared typically experience a smoother, faster process — and are far less likely to suffer price reductions or deal failure at this stage.

Financial Due Diligence

Financial due diligence is usually the most extensive workstream. The buyer's accountants will scrutinise your financial records to verify the accuracy of reported earnings, assess the quality of revenue, and identify any adjustments needed to arrive at a normalised profit figure.

Key areas examined include:

• Three to five years of statutory accounts and management accounts
• Revenue recognition policies and consistency
• Gross margin trends and cost of sales analysis
• Working capital requirements and cash conversion
• Normalisation adjustments to EBITDA (owner benefits, one-off costs, related party transactions)
• Debtor and creditor ageing analysis
• Capital expenditure history and future requirements
• Tax compliance, including VAT, PAYE, and corporation tax

Legal Due Diligence

Legal due diligence examines the legal framework of the business. The buyer's solicitors will review contracts, compliance, intellectual property, and potential liabilities.

• Company constitutional documents (articles of association, shareholder agreements)
• Material contracts with customers, suppliers, and partners
• Employment contracts, TUPE implications, and HR policies
• Property leases and freehold titles
• Intellectual property registrations and protection
• Litigation history and pending disputes
• Regulatory compliance and licensing
• Data protection and GDPR compliance

Commercial Due Diligence

Commercial due diligence assesses the market position, competitive landscape, and growth prospects of the business. This is particularly important for private equity buyers and trade acquirers entering new markets.

• Market size, growth rates, and trends
• Competitive positioning and differentiation
• Customer concentration and relationship strength
• Sales pipeline and revenue visibility
• Brand strength and reputation

Operational Due Diligence

Operational due diligence examines how the business functions day-to-day, including its systems, processes, supply chain, and technology infrastructure.

• Key operational processes and their documentation
• IT systems, software licences, and cybersecurity
• Supply chain resilience and key supplier dependencies
• Quality management and accreditations
• Insurance coverage and claims history

For UK mid-market transactions (businesses valued between £1 million and £25 million), due diligence typically takes between four and eight weeks. However, timelines vary significantly depending on the complexity of the business, the preparedness of the seller, and the buyer type.

A typical timeline might look like this:

• Week 1-2: Data room access granted; buyer's advisers submit initial information requests; preliminary document review begins
• Week 2-4: Detailed financial, legal, and commercial analysis; follow-up questions and clarifications; management meetings
• Week 4-6: Specialist reports (property, environmental, pensions, IT) if required; resolution of key issues identified
• Week 6-8: Final reports issued; price and terms confirmed or renegotiated; SPA drafting and negotiation intensifies

Well-prepared sellers with comprehensive data rooms can often accelerate this timeline significantly. Conversely, businesses with poor record-keeping or complex structures may see due diligence extend to three months or longer.

Preparing a comprehensive data room before due diligence begins is one of the most valuable things a seller can do. A well-organised data room signals professionalism, builds buyer confidence, and accelerates the process.

Essential documents typically include:

• Three years of audited or filed statutory accounts
• Monthly management accounts for the current and prior year
• Detailed profit and loss, balance sheet, and cash flow statements
• Corporation tax computations and returns
• VAT returns for the last three years
• PAYE and payroll records
• Bank statements for all business accounts
• Aged debtor and creditor reports
• Customer and supplier contracts
• Employment contracts and staff handbook
• Property leases or freehold title deeds
• Insurance policies and claims history
• IP registrations (trademarks, patents, domain names)
• Company registers (shareholders, directors, PSCs)
• Health and safety records and risk assessments
• Environmental compliance documentation
• IT infrastructure documentation and software licences

Even well-run businesses encounter issues during due diligence. The key is to identify and address potential problems before buyers discover them. Common issues that cause concern include:

• Financial inconsistencies: Discrepancies between management accounts and statutory accounts, or between tax returns and reported figures, raise immediate red flags
• Customer concentration: If one customer accounts for more than 15-20% of revenue, buyers will view this as a significant risk
• Owner dependency: Businesses that cannot function without the current owner are harder to sell and command lower multiples
• Undisclosed liabilities: Outstanding tax disputes, warranty claims, or pending litigation that were not disclosed in the information memorandum
• Contract issues: Key contracts with change-of-control clauses, or contracts that are not properly documented
• Employee issues: Missing employment contracts, non-compliance with auto-enrolment pensions, or potential TUPE complications
• Property problems: Lease terms that are unfavourable, approaching expiry, or contain restrictive clauses
• Regulatory non-compliance: Gaps in required licences, certifications, or data protection compliance

Each of these issues can lead to price reductions, additional warranties and indemnities, or in the worst case, the buyer walking away from the deal.

The best time to prepare for due diligence is well before you go to market. Here are the key steps every seller should take:

• Conduct a vendor due diligence exercise: Engage your own accountants and lawyers to review the business as a buyer would. This identifies issues early when they can be resolved without deal pressure
• Organise your data room: Set up a virtual data room and populate it with all key documents, logically organised by category. Index everything clearly
• Clean up your financials: Ensure management accounts reconcile to statutory accounts. Identify and document all normalisation adjustments
• Review all contracts: Check for change-of-control clauses, expiry dates, and any terms that might concern a buyer
• Address known issues: If you know about a problem — a pending dispute, a compliance gap, an expired licence — deal with it before going to market
• Brief your management team: Key managers will likely be interviewed during due diligence. Ensure they understand the process and are prepared
• Appoint experienced advisers: Work with a broker and solicitor who have M&A experience. They will anticipate buyer questions and help you present information in the most favourable light

Remember: due diligence is not something that happens to you — it is something you can actively manage and influence. Sellers who invest time in preparation consistently achieve better outcomes, faster completions, and fewer price adjustments.