We spend more time debating whether the numbers are correct than what they tell us we should do.
Within three months, leaders had a cost plan they could manage performance against. The team could keep producing it because the calculations lived in the standard tool again, not in one person’s head.
weekly cost estimate variance 8% 0.5%
Rebuild understanding, not the system .
Fixing today’s errors left no time to understand why they kept happening, so they kept happening. The first move was not to rebuild anything. It was to make the existing logic visible, so the team could rely on what they already had.
Directors were no longer debating a number. They were manually reconstructing the maths themselves to work out what the cost plan should say, because they could no longer trust the version the process produced. Underneath that, two waves of turnover had taken business and system knowledge with them, and the legacy planning tool had received limited support while a replacement was being built. People filled the gaps with manual workarounds, and each workaround buried its logic inside one person’s file, introduced a few more errors, and made the team more dependent on whoever had written it.
Wait for the replacement platform and live with a plan nobody fully trusted until it arrived. Or pull engineering effort back into a tool everyone had already agreed was on its way out. Neither addressed the actual problem: the organisation could no longer explain its own planning logic, and a new system built on top of that same gap in understanding would carry the same uncertainty forward.
The team was too busy explaining and correcting this week’s errors to recover the underlying logic, ease the manual burden, or prepare properly for the replacement. The long-term platform was still the right answer, but only once the business could explain what the current logic actually did and define what the new system needed to do instead. The first move was to check whether an approach already trusted in Europe could transfer here, which showed the North American system ran on comparable underlying logic. A lightweight AI interface then let business experts interrogate the existing code directly, without reading thousands of lines of code. Plan assumptions, outputs, and actual cost drivers were brought together in one new database table they could all see.
Business experts could see for themselves where the logic diverged from how the operation actually worked, without waiting on an engineer to translate it for them. Engineers knew where to target fixes to implement revised business logic. That cut the team’s dependence on individual spreadsheet authors and freed capacity to prepare the replacement properly rather than firefight around it. Within about three months, forecast variance fell from 8% to under 0.5%, the next planning cycle landed on time, and the team could move the replacement forward from a clearer shared understanding.