A synergy amount on a sheet is a claim. Substantiation only begins when someone can explain where the number comes from, who stands behind it, and how you can see whether it is actually happening. Without those three, a synergy is a wish that happens to have an amount attached.
Every synergy amount rests on an assumption about the world: that two sales teams can serve each other's customers, that a warehouse becomes redundant, that a system can be phased out without loss of functionality. That assumption is the actual subject. The amount is a derivative of it, calculated on the basis of the assumption and a few parameters.
Anyone who discusses the amount without naming the assumption is discussing nothing. Which assumption underlies your synergy amount is therefore the first question, not a detail that follows later. If the assumption has not been made explicit, there is also nothing to check against once practice turns out differently than expected.
Every synergy amount that appears on a list without a name attached remains a bookkeeping entry. There is no one who has to make it land, no one who explains why it fails to materialize, no one who is allowed to revise it when the assumption turns out to be wrong. Ownership is not a formality filled in afterwards; it is part of the substantiation itself. A synergy without an owner is by definition not substantiated, no matter how precisely the amount has been calculated.
What ownership concretely entails, and why it does not automatically end up with the CFO or the integration manager, is described on who owns a synergy. The short version: the owner is the person best able to judge the assumption and with the most influence over execution, not the person who sounded most convincing during the deal discussion.
An assumption that was valid at signing can be outdated three months later. A customer has left, a system turns out to be more complex than expected, a team is smaller than assumed. Substantiation is not a snapshot at the start; it is something that happens repeatedly, with a fixed question: does the assumption still hold.
How that check works and at what frequency it makes sense is described on how do you check whether a synergy is still achievable. Without that repetition, the first substantiation becomes the only one, and an outdated assumption remains the starting point for decisions it no longer fits.
Substantiating without tracking is a starting point without a follow-up. Tracking a synergy should not only show that it is on schedule, but also, and especially, when it is not. A traffic-light system in which everything is permanently green tracks nothing; it only confirms what people already hoped for.
How do you track synergies with traffic lights describes a way to keep status, owner and assumption together, so that a synergy that is slipping becomes visible before it is too late to correct course. And for the synergy that ultimately does not land, there is a separate question that must not be skipped: what do you do with a synergy that does not land does not ask you to quietly drop the amount, but to state why the assumption was wrong and what that means for the rest of the plan.
Substantiating is not just adding up what seems achievable. It should also include the question of whether a synergy is worth integrating for: some savings do not outweigh the risk of merging two systems, forcing two cultures into one process, or two teams that are just starting to function. A synergy that looks good on paper can cost more in execution than it delivers. That trade-off belongs with every amount, not as an exception but as a standard step.
The synergy baseline and the accompanying benefit tracking in the integration office are intended to enforce this structure: no amount without an assumption, no assumption without an owner, no owner without a recorded measurement point. The tool asks the questions and keeps track of status. It does not prove experience and it does not guarantee an outcome; it ensures that a synergy remains traceable instead of disappearing into a spreadsheet that no one opens again after the first month.
The tool is under construction. Anyone who wants to use it once it becomes available can sign up for the waiting list.
A synergy that revolves around personnel costs, merged teams or transferred tasks ultimately comes down to work: who does what, and how much of it remains after the integration. Anyone who wants to substantiate that with more than an estimate can use the work scan from FTE TO AI. It calculates, per task, which part of the work can be taken over by AI, providing a basis for the part of the synergy that runs on labor rather than on systems or real estate.
Vraag maar wat er op Day 1 moet staan, of wat integreren juist kapotmaakt.
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