The platform has made three add-ons in two years. On paper the group has consolidated purchasing, shared services, and cross-selling. In practice it runs four accounting systems, four email domains, four managed service providers, and a finance team that spends the first week of every month reconciling.
The synergies in the model were real. They were also conditional on an integration that nobody scoped.
Day one, day ninety, and the rest
Integration work sorts into three horizons, and confusing them is the most common planning error.
Day one is about not breaking anything and not creating a security hole. People can log in, email flows, payroll runs, and the acquired company's departing employees can actually be offboarded. Very little should change on day one. The goal is continuity plus control.
The first ninety days are about visibility and identity. One directory, one way to grant and remove access, and a single view of the combined financials even if the underlying systems remain separate. This is where the reporting synergy actually lands, and it does not require a systems migration to achieve.
Everything after that is the expensive part: consolidating ERP, warehouse systems, CRM. This is where the operational synergies live, and it should be driven by contract renewal dates and by the value case, not by a preference for whichever platform the biggest entity happens to run.
Most integration plans try to do the third horizon first and stall.
The diligence question nobody asks about the seller's contracts
Before close, somebody should read the target's technology contracts for three things: renewal dates, notice windows, and change of control provisions.
Notice windows are the one that costs money. A three-year MSP agreement with a ninety-day notice period that renews six weeks after close is a decision you have already lost if nobody read it. Discovering the same thing in month five means another full term at a price nobody negotiated.
Change of control clauses matter differently: some licences do not transfer, some trigger a repricing, and finding that out during an audit rather than during diligence is expensive.
Where the synergy actually comes from
In our experience the technology synergies in an add-on are, in descending order of reliability:
Duplicate software. Two CRMs, two e-signature tools, two expense platforms. Real, quick, and almost entirely a matter of picking one and running the renewal calendar.
Provider consolidation. Four MSP contracts at four price points, with four different scopes. Consolidating gets a better rate and, more importantly, one accountable party.
Infrastructure. Slower and smaller than most models assume.
ERP consolidation. The largest number in the model and the least reliable. It is a multi-year programme, it consumes management attention that the commercial plan also needs, and it should be justified on its own merits rather than assumed.
The thing that actually determines success
Not the plan. The owner.
Integration work spans functions, has no natural home, and competes with commercial priorities every week. Without one senior person accountable for it, with the sponsor's backing and enough context to make trade-offs, it degrades into a list that gets discussed and not done.
That person does not need to be full-time. They need to be senior, independent of the vendors, and present at the same cadence as the deal team.