Post-merger plans are written by the people who can see the systems. That is why the budget has a line for the ERP migration and no line for the other thirty-eight things that decide whether the deal works.
01 What integration usually means in the plan
Systems, people, premises, brand. Four workstreams, a Day-1 checklist and a synergy target. It is a plan for the things visible on a balance sheet and an org chart, and it is not wrong. It is just short.
02 What actually has to be integrated
Decision rights - who can approve what, at what value, from when. Governance - which board sees which risk. Process - two ways of doing the same thing, one of which has to win, and the reasons the losing one existed. Data - not the migration, the definitions: whether “active customer” means the same thing in both companies. Then risk appetite, supplier contracts and the terms hiding in them, pricing authority, and incentive schemes, which will quietly tell everyone what the new company actually values. Then capability, culture, and the informal network that makes the acquired business work and appears on no chart.
Each of those is a dimension. Each can sit at a different level of maturity in the two organisations. And each has a position in the order.
03 The order matters more than the list
Integrate processes before decision rights and you get a process nobody is allowed to approve. Migrate data before agreeing definitions and you get one system carrying two meanings, which is worse than two systems. Announce the target operating model before the incentive scheme matches it and the scheme wins. Sequencing is most of the craft, and it is the part that generic integration checklists cannot give you.
04 The hundred days are a programme, not a checklist
Day 1 is a readiness event: the lights stay on, people get paid, customers are told. The hundred days that follow are where value is either captured or quietly lost, and they need governance, a plan with owners and dates, and a way of knowing whether behaviour has actually changed. Run them as a checklist and you will complete every item and integrate nothing.
05 What to do before you sign
Run the same dimension triage on the target that you would run on yourself. You are not looking for a clean bill of health. You are looking for the three dimensions where the two organisations are furthest apart, because that is where the integration cost actually sits - and it is almost never in the systems.