An excerpt from an organizational brainstorming process on inorganic growth
The first 100 days after the deal
Written: 18.3.2025Updated: 15.10.2026עברית
Signing is not the finish line
The day after signing, it feels as if the hard part is over. The negotiation is done, diligence is closed, the announcement is out. In practice, this is where the part begins that decides whether the deal delivers the value it was meant to create.
McKinsey reviewed 248 large deals over ten years. Of the companies whose total shareholder return beat their market index in the first 18 months, 79 percent were still above it three years after close [1]. The early months do not decide everything, but they set the direction.
| Still above the market index | 79% |
|---|---|
| No longer above the index | 21% |
Two sides, the same 100 days
Integration plans are usually written from the buyer's point of view: synergies, systems, board reporting. Inside the acquired company, people ask different questions. Who do I report to now? What happens to my team? Is the way we have worked until now still worth anything? A good 100-day plan answers both lists.
| Phase | What the buyer does | What the acquired side needs |
|---|---|---|
| Days 1-30: stabilize | Appoints an Integration Management Office (IMO) with clear ownership. Issues one coordinated message to employees, customers, suppliers and the capital market. | To hear early and directly what changes and what stays. A personal conversation with every key person, not just a retention letter. |
| Days 31-60: plan | Maps processes and systems, overlaps and gaps. Chooses a model: full merger, partial, or standalone division. Builds a synergy plan with owners and timelines. | A seat at the mapping table. The people who know the customers and the product from the inside know what must not break. |
| Days 61-100: execute | Delivers first quick wins, merges critical systems and processes, reports to the board: what was achieved and what is at risk. | To see that what was said in month one is actually happening. This is where trust is built, or worn down. |
Culture is not an appendix
Sixty percent of acquirers said in hindsight that they should have put more resources into culture and change management [1]. Culture is not a slogan on the wall. It is how decisions get made, who speaks up in the meeting, and what counts as success. Gaps left unaddressed breed frustration and raise the risk that key talent will leave [2], taking with them the knowledge and relationships the company was bought for.
That is why culture gaps are worth diagnosing during due diligence, not after close. And the 100-day report to the board deserves a line on people: who is staying, who is undecided, and how customers feel.
Who leads it
Among companies that met their synergy targets, 76 percent staff integration with people who have the right skills, compared with 46 percent of those that met neither cost nor revenue targets [2]. The gap in shareholder returns between strong and weak integrators can reach 6 to 12 percentage points [2]. Choosing who leads the 100 days is a business decision, not only a staffing one.
In the brainstorming process this excerpt comes from, the 100 days were one chapter in a wider picture: why acquire at all, how to screen candidates, what to examine before signing, and how to measure afterward.
At Maya Shnur Advisory, I offer personal guidance in these deals from someone who knows every side, protects your side, and keeps sight of what truly matters and tends to get lost in a large transaction. maya-shnur-advisory.com
Sources
- Brian Dinneen, Christine Johnson, Alex Liu, "Post-close excellence in large-deal M&A", McKinsey & Company, June 2021. https://www.mckinsey.com/capabilities/m-and-a/our-insights/post-close-excellence-in-large-deal-m-and-a (opens in a new window)
- Rebecca Doherty, Oliver Engert, Andy West, "How the best acquirers excel at integration", McKinsey Quarterly, January 2016. https://www.mckinsey.com/capabilities/strategy-and-corporate-finance/our-insights/how-the-best-acquirers-excel-at-integration (opens in a new window)