Field notes
Dual-run checks without freezing reporting
Dual-run means old and new models produce comparable outputs for an agreed window. The goal is confidence, not perfection on every column on day one.
Start with the measures leadership quotes in meetings. If revenue and active accounts match within an agreed tolerance, secondary dimensions can follow in later waves.
Automate the comparison. Manual spreadsheet diffs do not scale and quietly get skipped under deadline pressure.
Keep a single source of truth for which model feeds which report during the window. Ambiguity here creates duplicate numbers in the same deck.
Our modernisation engagements treat dual-run duration as a priced workstream with an exit criterion, so the temporary complexity does not become permanent.