Due diligence checklist: guide to buying a business

Published Tuesday 21 April 2026

Table of contents

• What is due diligence when buying a business?
• Why is due diligence important?
• Essential due diligence checklists before buying a business
• Key documents to review during due diligence
• FAQs on due diligence when buying a business

Key takeaways

• Review at least three to five years of financial records, including tax returns, profit and loss statements, and cash flow data, to verify the true financial health of any business before you buy it.
• Investigate legal, operational, and regulatory risks separately using dedicated checklists, as each area uncovers different problems that could affect the value or viability of the business.
• Work with a lawyer and accountant throughout the due diligence process, since professional guidance helps you spot hidden liabilities, meet compliance requirements, and avoid costly mistakes after the deal closes.
• Use due diligence findings as a negotiating tool — if serious issues come to light, you can renegotiate the price, ask the seller to fix problems, add protective clauses to the agreement, or walk away entirely.

What is due diligence when buying a business?

Due diligence is your comprehensive investigation of a business before you buy it. This research and analysis verifies the business is what it claims to be and worth your investment.

Whether you're buying an online business, small business, or larger company, due diligence protects you from costly mistakes. For example, you might fail to provide investors with a Product Disclosure Statement when making regulated offers to fund acquisitions.

Due diligence gives you confidence to proceed with the purchase, renegotiate terms, or walk away entirely. Your checklist should confirm the business has measurable commercial potential and aligns with your goals.

Why is due diligence important?

Due diligence protects you from costly mistakes when acquiring a business by uncovering risks before you buy. While sellers must represent their business accurately, it's your responsibility to verify everything.

Thorough due diligence ensures you're making a sound decision, paying a fair price, and meeting regulatory requirements. It helps you avoid discovering serious problems after the deal closes, such as:

• hidden liabilities or overstated earnings
• unreported debts, tax implications, or unreliable revenue sources
• legal issues or regulatory non-compliance, which might result in fines or even business closure
• operational inefficiencies, outdated systems, or fragile supplier or customer relationships
• hidden reputational issues or market weaknesses

Seek expert advice with your due diligence checklist, especially for legal and financial matters.

Essential due diligence checklists before buying a business

These due diligence checklists help you systematically evaluate every critical aspect of a business purchase. Each checklist focuses on a specific risk area to ensure you don't miss important details.

Work with a lawyer for legal matters and a financial advisor for complex financial analysis.

Financial due diligence

Financial due diligence verifies the business's true financial health and profitability. Official standards like New Zealand International Financial Reporting Standard (NZ IFRS) 3: Business Combinations help define what constitutes a 'business' for reporting purposes, though Public Benefit Entity (PBE) IFRS 3 applies to public benefit entities.

Key financial areas to investigate:

• Historical performance: Review three to five years of tax returns, financial statements, cash flow records, and profit and loss statements
• Tax compliance: Confirm current tax status and identify any outstanding liabilities, keeping in mind that provisional tax payments may be due on 7 May for businesses with a March balance date
• Debt analysis: Check for outstanding debts, loans, and other financial obligations
• Cash flow assessment: Analyse current cash flow patterns and growth potential
• Industry benchmarks: Compare revenue trends against industry projections and standards

Legal due diligence

Legal due diligence uncovers legal risks and confirms the business operates within regulatory boundaries. Under clause 12 of Schedule 3 of the Financial Markets Conduct (FMC) Regulations, a Key Information Summary (KIS) must include a summary of the 'most significant' risks.

Essential legal investigations:

• Contract review: Examine all supplier, customer, employee, and operational agreements plus leases
• Intellectual property audit: Verify ownership and value of patents, trademarks, copyrights, and trade secrets
• Registration verification: Confirm business name, domain, and trademark registrations are valid and transferable
• Litigation assessment: Investigate any past, current, or pending lawsuits and legal disputes

Operational due diligence

Operational due diligence evaluates how the business runs day to day, including its systems, staff, and processes. Use this checklist to cover all aspects of business continuity:

• review business plans and strategy documents
• evaluate the business's operations and processes, including management structures, staffing, and human resources
• assess customer and supplier relationships and contracts
• review business assets and equipment, considering their age, maintenance schedules, and anything needing repair
• examine the business technology infrastructure, data security, and software systems to make sure they're up to date, secure, and scalable

Analysing market position and competition

Analysing market position and competition helps you understand a business's true value so you can agree to a fair price. This checklist examines how, to whom, and where the business sells its products or services. It also assesses the business's position compared with competitors and its opportunities for growth.

• Review market strategy plans and performance reports
• Check out the business's online presence, including search rankings, its existing ad buys, and other marketing campaigns
• Perform a competitor analysis to understand the business's challenges and opportunities, and the strength of the business in its market
• Evaluate how the business reaches its customer base, and customer loyalty
• Review customer records, feedback, and reviews

Regulatory and compliance

Regulatory and compliance due diligence examines the regulatory challenges the business faces and checks that it meets its obligations and statutory requirements. Laws and regulations vary by industry, country, and region.

• Review regulatory and compliance obligations specific to the industry
• Check for issues related to licences, permits, premises, or government regulations
• Review tax compliance status, including tax records, liabilities, and compliance with local and international tax laws, noting that professional standards evolve. For example, recent code revisions for accountants will strengthen ethical expectations for tax planning activities in New Zealand, applying to New Zealand resident members and other practitioners from 1 July 2025.
• Review compliance with workplace conditions, agreements, and employee entitlements
• Investigate whether the business follows environmental regulations, and check its potential liabilities in areas like waste management, pollution, and hazardous materials

Key documents to review during due diligence

Reviewing documents is fundamental to thorough due diligence. These records provide concrete evidence to verify claims made by the seller and reveal potential issues.

Your document checklist will include financial records, contracts, legal documents, sales reports, and customer records. The specific documents vary by industry and location, so work with an accountant, lawyer, or business broker to ensure you haven't missed anything critical.

Financial and tax

• Tax returns (three to five years)
• Profit and loss statements (three to five years)
• Balance sheets (three to five years)
• Audit reports
• Business credit reports
• Bank loans or other finance
• Leases
• Sales records
• Business valuations

Equipment, assets, and stock

• Plant, equipment, or vehicle leases
• Maintenance records
• Other assets owned or leased
• Outstanding debts to suppliers
• Stock
• Software licences

Legal

• Insurance contracts
• Regulations or compliance issues
• Legal proceedings
• Mandatory codes of practice
• Business standards and procedures
• Legal agreements for directors, partners, or shareholders
• Privacy requirements
• Data management processes

FAQs on due diligence when buying a business

Here are answers to common questions about due diligence when buying a business.

How long does due diligence take when buying a business?

Due diligence typically takes 30 to 90 days, depending on the size and complexity of the business. Smaller businesses may require less time, while larger acquisitions with multiple locations or complex operations need more thorough investigation.

What happens if due diligence reveals problems?

If due diligence uncovers significant issues, you have several options. You can renegotiate the purchase price to reflect the risks, request that the seller fix the problems before closing, add protective clauses to the purchase agreement, or walk away from the deal entirely.

Do I need a lawyer for due diligence?

Yes, you should work with a lawyer for legal due diligence. They can review contracts, identify legal risks, verify compliance with regulations, and ensure all documentation is properly structured to protect your interests.

How much does due diligence cost?

Due diligence costs vary based on business size and complexity. Expect to pay for professional services including lawyers, accountants, and industry specialists. While costs can range from a few thousand to tens of thousands of dollars, this investment protects you from potentially much larger losses.

What's the difference between financial and legal due diligence?

Financial due diligence examines the business's financial health, including revenue, expenses, debts, and cash flow. Legal due diligence focuses on contracts, compliance, intellectual property, litigation risks, and regulatory requirements. Both are essential for a complete assessment.