After an acquisition the data is rarely missing. Each company answers the same question in its own vocabulary: one runs SAP, one runs Dynamics, one runs something a local team built. Cost centres do not line up, and one supplier is three records across the group.
Supplier spend usually shows it first. The same supplier appears under its legal entity, a brand name and an old company name, so the group can miss a rebate threshold it has already crossed. Intercompany invoices counted as external spend inflate the procurement baseline the other way.
The usual fix is a consolidation workbook that one controller maintains. It breaks when it has to scale, when that person is away, or when someone asks how a number was derived.
We connect each company's systems read-only and keep a source-faithful copy of what came out. Shared definitions become mapping tables, SQL and rules you can review. When two records are treated as one, the evidence stays attached.
The first deployment covers one operating group and its subsidiaries, not a pooled raw-data environment across unrelated portfolio companies. That keeps the data model honest and the isolation questions simple.