The 8 Stages of an M&A Deal, and the People Question Hiding in Each One

Last reviewed: October 29, 2026.

Short answer: Every M&A deal moves through eight stages: sourcing and thesis, screening and approach, due diligence, signing to close, Day 1 readiness, the first 100 days, full integration and value capture, and an optional post-close review. Finance, legal and tax have a playbook for each one. The people side usually doesn't. At every stage there's a predictable people pain point and one question the deal team should be able to answer before moving on, such as "Does our thesis depend on the target's people working differently from how they work today?" or "Can these two sales teams actually sell together?" Behavioural data, read at team level, is how you start answering those questions with evidence instead of instinct.

Picture a deal from the inside.

A deal partner falls in love with a thesis on a Tuesday. By Friday the model shows the synergies. Six months later, two sales teams who were supposed to cross-sell are sitting on different floors, using different playbooks, quietly waiting for the other side to make the first move. Nobody did anything wrong. The people question just never got asked at the moment it could have changed something.

Here's the full lifecycle, stage by stage: what usually goes wrong on the people side, who's deciding at that point, and the question behavioural data can help answer. For a broader view of how people insight changes across the deal, see Human Capital Intelligence at Each Stage of a Deal.

Stage 1: Sourcing and thesis. Does the thesis depend on people changing?

Who decides: The deal partner or head of corporate development, and the investment committee.

This is where the story of the deal gets written. And it's often written as if the target's people were a constant.

What usually goes wrong:

• The thesis assumes the target's people can scale or change, without asking whether they work that way today.
• People questions are left to diligence, after the thesis is already fixed.
• Culture is judged from a few founder meetings.

A thesis that says "we'll professionalise their sales motion" or "we'll plug them into our platform" is a thesis about behaviour. If the people would have to work differently to deliver it, that's the biggest assumption in the deal, and it's usually the least examined.

The key question: Does our thesis depend on the target's people working differently from how they work today?

Who can be assessed: Not the target yet. But the buyer can read its own deal team and the teams that would receive the target. That alone shows whether the people expected to absorb the deal are built for the change the thesis assumes.

Stage 2: Screening and approach. Will their leadership work the way our plan assumes?

Who decides: The deal partner and corporate development, mostly through management meetings.

This is the courtship stage. Everyone is on their best behaviour, and that's exactly the problem.

What usually goes wrong:

• Management presentations are rehearsed, so it's hard to see how the leadership team really decides together.
• The relationship rests on chemistry between two or three people at the top.
• Early signs of friction, such as differences in pace or formality, get waved away.

You leave the meeting saying "great team." What you've actually seen is a great presentation. The friction you noticed, and decided didn't matter, is often the first preview of integration.

The key question: Will the target's leadership work at the pace and in the way our plan assumes?

Who can be assessed: Usually nobody on the target side. At most the leadership team, if it agrees. On the buyer's side, the same teams as in stage 1.

Stage 3: Due diligence. Can their leadership and key teams deliver the thesis?

Who decides: The investment committee and deal team, with advisers.

Diligence is where the most effort goes, and where the people side is most often reduced to paperwork.

What usually goes wrong:

• People diligence stops at org charts, contracts and key-person lists. How teams actually work isn't checked.
• The teams the synergies depend on, such as sales and operations, aren't seen until after close.
• Findings arrive too late to shape the 100-day plan.

An org chart tells you who reports to whom. It doesn't tell you how that leadership team makes a hard call on a Thursday night when two priorities collide. And the team that has to deliver the cross-sell? Often nobody meets them before the deal closes. This is the gap behavioral due diligence is designed to close.

The key question: Can the target's leadership and key teams, as groups, deliver the thesis?

Who can be assessed: The target's leadership team as a group (five or more people, with consent), sometimes one or two key teams, plus the buyer's receiving teams. The read covers the group, never individual ratings.

Stage 4: Signing to close. Is the integration plan built for how these teams actually work?

Who decides: The integration lead and the integration office being formed, and the designated steering committee.

The ink is dry, but the deal isn't done. This is the limbo window, and it's louder inside the organisation than it looks from outside.

What usually goes wrong:

• Uncertainty and rumours spread while contact between the two sides is limited by law.
• The integration plan is written by the buyer alone and sequenced before anyone knows how the teams work.
• The steering committee forms without agreeing how it will decide.

The integration plan is often the most detailed document in the deal, written by people who have barely met the teams it describes. Meanwhile the corridor is filling the information gap with rumours. For more on what leaks in this window, see The Pre-Close Window, and for the hand-off itself, the handover problem between deal and integration teams.

The key question: Is our integration plan sequenced for how these teams actually work?

Who can be assessed: All of the buyer's teams. On the target side, leadership and teams where clean-team rules allow, which is often still limited.

Stage 5: Day 1 readiness. Is each team ready to hear the message, and do we know who decides what?

Who decides: The integration office lead, the steering committee and the communications lead.

Day 1 is a single moment that every team experiences differently.

What usually goes wrong:

• Announcements are written in the buyer's voice and land differently in each team.
• Decision rights are unclear on Day 1, so decisions stall or go round in circles.
• Customer-facing teams are briefed late, so customers hear mixed messages.

The same email lands as reassurance in one team and as a threat in another. And if nobody knows who can sign off on what, the first week is spent escalating questions rather than answering them. Customers notice before the steering committee does. See How to Announce an Acquisition to Employees for the communication side, and Choosing the Leadership Team After a Merger for decision rights at the top.

The key question: Is each team ready to hear and act on the Day 1 message, and do we know who decides what?

Who can be assessed: As in stage 4. The full target teams are usually reachable from Day 1.

Stage 6: The first 100 days. Can these teams actually work together?

Who decides: The integration office, workstream leads, the steering committee and, in PE deals, the operating partner.

This is where the plan meets reality, and where the quiet failures happen.

What usually goes wrong:

• Joint work such as cross-selling or shared procedures is assumed to start on schedule. When one team works differently, it stalls quietly.
• Hand-offs between the two organisations break.
• Steering decisions are slow, or fast without weighing the options.
• Problems only show up when milestones are missed.

"Quietly" is the key word. Nobody announces that the cross-sell has stalled. The pipeline just doesn't build. By the time a milestone is missed, the cause is weeks old. More on this in what AI can see in the first 100 days of integration.

The key question: Can these two sales teams actually sell together, and where does the plan need a nudge?

Who can be assessed: Full teams in both organisations, five or more people each. Take a baseline, then read the same people again at Day 90 so the change is visible.

Stage 7: Full integration and value capture. Are the combined teams converging?

Who decides: The CEO of the combined business, the operating partner and the board.

The integration office starts to step back. This is where you find out whether the change was real.

What usually goes wrong:

• Momentum fades after the first 100 days and integration fatigue sets in.
• Old ways of working come back once the integration office steps back.
• Combined teams still behave as two organisations.

On paper it's one company. In the meetings it's still "us" and "them." The new processes are documented. The old habits are practised.

The key question: Are the combined teams converging on one way of working?

Who can be assessed: Combined teams of five or more, read again regularly, for example every six months.

Stage 8: Post-close review (optional). What did the people side teach us?

Who decides: The deal partner, the investment committee and corporate development.

The stage most acquirers skip, and the one that compounds across deals.

What usually goes wrong:

• Lessons stay in people's heads, so the next deal repeats the same mistakes.
• There's no record of which people-side patterns went with a smooth integration or a difficult one.

Serial acquirers have models for everything except the thing that keeps surprising them.

The key question: What did the people side of this deal teach us for the next one?

What feeds it: Earlier reads from this deal, plus the client's own notes on how the integration went.

The whole lifecycle at a glance

How should behavioural data be used across the deal?

The questions above only help if the answers are trustworthy and used responsibly. At HumanaQ we work to a few ground rules at every stage:

• Team level only. At least five people per team, and nobody named.
• Never for selection, retention, pay or performance decisions. This is about how groups work, not about judging individuals.
• No flight-risk predictions.
• Patterns, not causes. Behavioural patterns tend to go with outcomes; we don't claim they cause them.
• Leadership reads are for the group. In diligence, the leadership team is reported as a group, never as ratings of individuals.
• Consent and legal limits. The buyer's own teams can take part at any stage; the target's people only with their consent and within the deal's legal limits.

Used this way, behavioural data doesn't replace the deal team's judgement. It gives that judgement something solid to work with, at the moment it can still change the thesis, the price, the plan or the first 100 days.