Business due diligence for buying and selling a business

Business due diligence is a critical stage when buying or selling a business. It’s where buyers verify key information, assess risk, and confirm that the deal terms and price accurately reflect the business. While the process can be demanding, good preparation can help avoid delays, renegotiations, or unexpected issues.

In this guide, we explain business due diligence in the UK and what buyers and sellers should expect, including:

• What business due diligence is and why it matters
• What buyers check during due diligence
• The business due diligence process and typical timelines
• How long due diligence takes and what can delay it
• Types of due diligence
• Due diligence statement (what it is & what it includes)
• A practical business due diligence checklist
• FAQs on pricing, risk, and next steps

What is business due diligence?

Business due diligence is the process of checking a company’s financial, operational, and legal position when buying a business. It involves a thorough review of the business’s legal structure and key information, helping to ensure the seller has provided an accurate representation of the company.

What do buyers check in due diligence?

During due diligence in acquisitions, a seller will be presented with many legal due diligence enquiries that help a buyer to gather evidence and confirm key assumptions. Requests typically focus on the business’s financial and legal position, including:

• certifications and regulatory compliance
• insurance
• employee contracts and key staff terms
• client relationships and major contracts

Buyers focus on these areas because they reveal potential legal and operational risks, test whether the business can continue to operate smoothly after completion, and help validate the long-term value of the acquisition.

Buyers may also look at sector and competitor research to validate the valuation and identify risks such as customer concentration or reliance on a small number of suppliers.

Business due diligence process (UK): what happens and when?

Due diligence in mergers and acquisitions usually starts after heads of terms are agreed. The buyer shares a due diligence request list, and the seller provides documents and written responses, often via a secure data room.

The buyer then reviews the information, asks follow-up questions, and uses the findings to validate the agreed price and agree final deal terms.

In practice, the business due diligence process usually looks like this:

1. Scope agreed: what will be reviewed (financial, legal, operational and commercial)
2. Information shared: documents provided and initial questions answered
3. Review and follow-ups: buyer tests assumptions and requests clarifications
4. Findings summarised: issues and risks are documented in a due diligence report
5. Deal terms finalised: outcomes are reflected in the contract, ensuring the agreed price and terms accurately reflect the information reviewed and that appropriate protections are in place for both parties

Due diligence when buying a business

When buying a business, due diligence helps the buyer confirm whether the company is as described and understand any key risks before committing. Buyers typically focus early on contracts, liabilities, compliance, customer concentration, supplier dependency and key-person risk.

Due diligence when selling a business

When selling a business, the goal is to keep the process as efficient as possible to reduce the risk of delays or renegotiations. Preparing key documents ahead of time and responding quickly to follow-up questions can help speed up due diligence and maintain buyer confidence.

Preparing your business financially for sale

The video below outlines the key financial considerations sellers should address before entering due diligence. Preparing early helps reduce delays, supports buyer confidence and lowers the risk of price renegotiation later in the process.

How long does due diligence take when buying a business?

Timelines vary depending on the size of the business and the complexity of the deal, but due diligence when buying a business often takes around 4-10 weeks from the initial request list to agreed findings and final legal terms.

Smaller and better-prepared transactions can move faster, while more complex acquisitions (such as regulated sectors, overseas elements or incomplete records) can take longer.

Signs due diligence is likely to take longer include:

• documentation is incomplete or poorly organised
• there are complicated contracts, tax issues or ongoing disputes
• the buyer needs specialist reviews (e.g., legal, financial, HR, IT)
• issues are uncovered that require negotiation or fixes before completion

If you’re selling your business, preparing a clear due diligence pack in advance and responding quickly to follow-up questions can help keep the process moving and reduce risk of delays or price renegotiations.

Types of due diligence

In corporate due diligence (including M&A due diligence), buyers may use a mix of ‘hard’ and ‘soft’ checks, with enhanced due diligence used in higher-risk situations.

Hard due diligence

Hard due diligence focuses on the evaluation of concrete data that is, typically, easily obtainable. This is a common process that consists of a fundamental analysis of financial statements, including:

• balance sheets
• projections
• income statements

Additional factors include reviewing ongoing litigation and subcontractor relationships. Hard due diligence is driven by mathematics and legalities.

Soft due diligence

Soft due diligence looks beyond the numbers at the people and relationships that keep the business running. This includes the management structure, culture, and key-person risk, as well as the strength and stability of the customer base. It helps balance the financial review so important non-financial risks aren’t missed.

Enhanced due diligence (EDD)

Enhanced due diligence (EDD) involves deeper checks where the risk profile is higher – for example, businesses subject to financial regulation or supervised by the Financial Conduct Authority (FCA), transactions with links to high-risk jurisdictions, or situations involving politically exposed persons (PEPs).

Factors leading to EDD include:

• Higher-risk countries and business sectors
• Complex or opaque beneficial ownership structures
• Unusual transactions that lack an obvious economic or lawful purpose

Business partner screening

Business partner screening is a form of corporate due diligence used to assess third parties the business relies on, such as partners, joint venture participants, or key suppliers.

It helps identify legal, financial, or reputational risks by building a clearer picture of a counterparty’s background. In the context of mergers and acquisitions, business partner screening can support wider M&A due diligence by highlighting third-party risks that may affect operations or value after completion.

Due diligence statement (what it is & what it includes)

When providing documents to support the buyer’s investigation, sellers will produce a due diligence statement. This document provides an overview of all materials used during the business due diligence process, confirming that a seller has prepared all relevant materials to the best of their knowledge.

A due diligence statement typically includes:

• Identification procedures – checks to verify the identity of the individuals and entities involved in the transaction
• Sanctions list checks – screening to confirm that parties are not subject to UK or international sanctions
• Risk assessments – an evaluation of potential financial crime, regulatory, or reputational risks linked to the transaction

Business due diligence checklist

During due diligence in mergers and acquisitions, buyers will typically review:

• Finances: company accounts, annual reports, expenses, payroll, and forecasts
• Legal: insurance policies, regulatory compliance, key supplier/customer contracts and tax returns
• Operations: how the business runs day-to-day (sales process, products/services, and marketing activity)
• Assets: property and equipment, fixed/variable assets, and intellectual property rights
• Employees: contracts, structure, salaries and subcontractor relationships

Business due diligence FAQs

What documents does a seller need for business due diligence?

As a seller, you should be prepared to provide a wide range of financial, legal, and operational documents during business due diligence, including:

• Financial: statutory and management accounts, tax returns, forecasts, and debt details
• Legal: customer and supplier contracts, employee agreements, leases, insurance policies
• Compliance & assets: licences, regulatory approvals, intellectual property details

Having these documents prepared in advance can help speed up due diligence when selling a business and reduce the risk of delays or price renegotiations.

What’s the difference between due diligence and business valuation?

Business valuation and due diligence are closely linked, but they have different purposes during a transaction.

A business valuation estimates what a business is worth based on its financial performance, assets, growth prospects, and market conditions.

Business due diligence comes afterwards, and checks whether the information behind the valuation is accurate and highlights any financial, legal or operational risks before the deal goes ahead.

In mergers and acquisitions, due diligence helps buyers to confirm that the agreed price is fair before they commit to completing the transaction.

What are common due diligence mistakes when buying or selling a business?

The most common due diligence mistakes include:

• Incomplete, outdated, or poorly organised documentation
• Failing to disclose known issues early on in the process
• Underestimating how long the due diligence process will take

Focusing only on financial data, and overlooking legal risks, operational weaknesses, or cultural or management issues

Avoiding these mistakes during a transaction helps keep business due diligence efficient and protects deal value.

Can due diligence change the agreed price?

In some cases, due diligence can lead to a discussion about price or deal terms if new information comes to light. This is a normal part of the transaction process and helps ensure the final agreement reflects a clear and accurate understanding of the business.

This typically happens only where significant issues are identified, such as:

• Undisclosed liabilities or tax exposures
• Declining margins or inaccurate forecasting
• Customer or supplier concentration risks
• Concerns with compliance

Importantly, not all findings lead to a price reduction. Many issues are resolved through practical solutions that protect both buyer and seller, including:

• Retentions or deferred consideration
• Warranties and indemnities
• Changes to deal structure

What happens if issues are found during due diligence?

If any issues are uncovered during the due diligence stage of a transaction, the buyer will assess their significance and work with the seller to understand context and potential solutions. Many issues are resolved without delaying or derailing the transaction, particularly where they are identified early and addressed proactively.

Depending on the nature of the findings, possible outcomes may include:

• Renegotiating the purchase price
• Requesting additional protection through contracts
• Requiring issues to be resolved before completion
• Restructuring the transaction

In rare cases, where material risks cannot be mitigated, a buyer may decide not to proceed. However, thorough preparation and professional support significantly reduce the likelihood of this outcome.

Do I need enhanced due diligence (EDD) for a UK business sale?

While enhanced due diligence (EDD) is not required for every UK business sale, it could be necessary in higher-risk situations, including:

• businesses operating in regulated sectors
• complex or opaque ownership structures
• links to high-risk jurisdictions
• involvement of politically exposed persons (PEPs)

EDD usually means more detailed checks on ownership, identity verification, and the source of funds, and you may be asked for additional supporting documents.

Expert due diligence with KBS Corporate

A buyer’s goal during due diligence is to confirm there are no unexpected issues, that the business is fairly priced, and that risk is clearly understood and appropriately managed.

When you choose KBS Corporate to sell your business, we help you prepare a due diligence report that highlights any key areas of concern early, allowing risk to be addressed and the right contractual protection put in place as you move into the legal process.

Due diligence requires experience, trust, and attention to detail, and our team works with you to keep the process efficient, confidential, and focused on ensuring it does not delay or negatively impact your sale.

Get in touch with our sales team to see how we can help with your transaction. You can also learn more about where due diligence fits in the wider context of a business sale in our expert guide on how to sell your business.