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Our expertisesWhat are the steps of an M&A due diligence?
9 Juillet 2026
In a merger or acquisition transaction (an M&A deal), M&A due diligence is the moment of truth. It is what turns an investment hunch into an evidence-backed decision — or surfaces the blind spots before it is too late. Done well, due diligence de-risks the transaction and fuels the negotiation.
This guide breaks down the steps of a due diligence, the different types involved, how long it takes, and the mistakes to avoid. It also includes our ready-to-use checklist, available for download.
What is an M&A due diligence?
An M&A due diligence (sometimes called an acquisition audit, or in a broader sense simply “due diligence”) is an in-depth review of a target company. It is typically conducted before an M&A transaction is finalized. Its purpose is to verify that what is being presented is real, to measure the risks, and to confirm the target’s actual value.
In practice, the acquirer and its advisors go through the target’s financials, contracts, tax position, teams, operations, and market with a fine-tooth comb. The point is not only to surface bad surprises: it is also to objectively assess the value-creation potential post-transaction.
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Where does due diligence fit into the M&A process?
Due diligence is not a standalone step. It sits within a well-defined transaction sequence. Understanding where it fits helps you prepare it better.
An M&A process typically follows six major phases:
- Initial contact between seller and acquirer.
- Signing of a letter of intent (LOI), which formalizes the interest and the indicative terms.
- Due diligence itself, the in-depth investigation phase.
- Final negotiation, adjusting price and reps & warranties based on the findings.
- Signing of the definitive agreements.
- Closing, when the transaction is actually completed.
Due diligence therefore sits between the letter of intent and signing. It is what feeds the negotiation.
The 6 steps of an M&A due diligence
Whatever the size of the deal, the steps of a due diligence follow a consistent logic, from scoping to decision.
Here are the six key steps of the process:
This is the step where the seller gathers documents into a data room: a secure environment where the acquirer reviews the underlying documents.
In parallel, the acquirer mobilizes teams and advisors, sets the timeline, and prepares its request lists and questionnaires.
Document collection covers the gathering of source materials.
For example:
- Financial statements,
- Customer and supplier contracts,
- Leases,
- Board and shareholder minutes,
- Tax filings,
- Employment contracts,
- Ongoing litigation,
- Intellectual property.
The different types of due diligence to run
A due diligence is never monolithic: it breaks down into several complementary workstreams, each shedding light on one facet of the target.
The main types of due diligence are:
- Financial due diligence: reliability of the financial statements, asset quality, debt structure, and sustainability of performance over 3 to 5 years.
- Legal due diligence: major contracts, litigation, regulatory compliance, and intellectual property.
- Tax due diligence: tax filings, at-risk tax positions, and potential reassessments.
- Commercial due diligence: market positioning, pipeline strength, customer concentration and retention, growth outlook.
- Operational due diligence: process efficiency, supply chain, and value creation.
- IT due diligence: systems robustness, fit of the ERP/CRM stack, and cybersecurity.
- HR and people due diligence: management team, culture, compensation, and labor relations.
- Environmental due diligence (ESG): compliance, carbon footprint, and climate risks.
Buyer or seller: two perspectives
Due diligence can be initiated from either side of the deal.
- On the buy-side, due diligence is used by the acquirer to validate the investment.
- On the sell-side, a vendor due diligence is commissioned ahead of the sale: the seller audits its own company to anticipate questions, fix weaknesses, and strengthen its negotiating position.
How long does a due diligence take?
Two questions come up systematically before kicking off: how long will it take, and who will be involved? Both answers depend on the size and complexity of the transaction.
A due diligence typically takes between one and two weeks: shorter for a small deal, longer for a complex file.
Who runs a due diligence?
On the participant side, the acquirer surrounds itself with specialist advisors: financial experts and transaction services, corporate lawyers, tax advisors, and specialist firms for the commercial, HR, or IT workstreams. Coordinating these expertises is what conditions the quality of the final report.
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The 5 most common mistakes to avoid
A failed due diligence only shows up after closing, when the surprises start landing. A few mistakes come up more often than others:
- Starting the M&A due diligence too late, under calendar pressure, and rushing the analysis.
- Concentrating the effort on financial and legal work while neglecting commercial and human-capital angles. That is often where the real post-deal breakdown risks are hiding.
- Underestimating dependency on a handful of customers or a key executive.
- Working from an incomplete or disorganized data room, which stretches timelines and skews conclusions.
- Failing to link the findings back to the negotiation: an analysis that doesn’t translate into price adjustments or reps & warranties loses most of its value.
Download your M&A due diligence checklist
To make sure nothing slips through on your next transaction, we've compressed the essentials into a downloadable M&A due diligence checklist. It lists every document to gather and every item to verify — a ready-to-use tool to structure your data room or brief your advisors.
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