Why do our complex deal models keep breaking?
You built a model that works on the deals you understand. On the hard ones, it breaks — and you assume the formula is wrong. It isn't. Somewhere inside, an assumption is doing work no one checked. You and your team treat a guess as a fact. The growth rate someone typed in six months ago. The churn number borrowed from another deal. Nobody asked if it still held. That isn't a modeling failure. That's a habit you haven't built. The fix isn't a better spreadsheet. It's a practice: before the numbers run, someone in the room names each assumption and asks if it earned its place. Do that together, every time, and the complex deals stop breaking in ways you can't explain.
The model isn't broken. An assumption inside it is doing work you never checked. Find the inputs you treated as fact — growth rate, retention, timing — and test each one with your team before you trust the output again. Choose to question, not just calculate.
What changes unlock by starting
- A shared, visible list of every assumption behind the model.
- Fewer surprises when a deal shifts, because you tested inputs, not just formulas.
- A working habit of questioning inputs before trusting outputs, on every complex deal.
- A team that catches weak assumptions early, before the deal breaks in front of a client.