Ask a planner where their numbers come from and you will usually get an honest answer: a export, pasted into a sheet, adjusted by hand, then circulated. The sheet is not the problem. The copy is.
From the moment that export happens, the plan and the operation start to drift. An order gets amended. A material arrives short. A process is rerouted. None of it reaches the sheet until somebody remembers to redo the export.
What changes when the order is the source
If the plan is calculated from approved orders against configured BOMs, the arithmetic stops being manual and starts being derived.
- Material requirements come from the structure, not from memory
- Shortages appear against real available stock, including what is already reserved
- Process and machine load is calculated per stage rather than assumed
- Amending an order re-runs the plan instead of invalidating it
The reconciliation tax
Teams rarely measure how much time goes into making two systems agree. It hides inside everyone's week: a planner checking stock, a supervisor confirming a route, a manager rebuilding a report because the numbers moved.
That work does not disappear because someone is careless. It exists because the plan was built from a snapshot. Remove the snapshot and most of the reconciliation goes with it.
A reasonable first step
You do not have to replace the spreadsheet on day one. Run it in parallel against calculated requirements for a few weeks. Where the two disagree, the difference is almost always a rule nobody had written down — and that rule is the thing worth capturing.
