Before a single line of code is written or a dollar of budget committed, every venture is built on a stack of assumptions. Some are about customers — who they are, what they want, how much they will pay. Others are about the market — how large it is, how fast it moves, who else is competing for the same attention. Still others are operational — how long it will take to build, what it will cost to acquire a customer, whether the unit economics will hold.
The problem is not that founders make assumptions. That is unavoidable. The problem is that most assumptions are never written down, which means they are never examined, never tested, and never updated when reality disagrees with them.
Documenting your assumptions is not a bureaucratic exercise. It is a discipline that forces clarity. When you write 'We believe that small restaurant owners will pay $150 per month for automated inventory tracking,' you have done something important: you have made a falsifiable claim. You can now design an experiment to test it.
A useful assumption log has three columns: the assumption itself, the evidence you currently have for it, and the test you would run to validate or invalidate it. Keep it short. Ten to fifteen assumptions is usually enough to cover the critical unknowns in an early-stage venture.
Revisit the log at every major milestone. When an assumption is proven wrong — and some will be — treat it as a learning, not a failure. The goal is not to be right from the start. The goal is to be wrong quickly and cheaply, so you can adjust before the cost of being wrong becomes prohibitive.
The founders who build durable businesses are not the ones who had perfect insight at the outset. They are the ones who stayed honest about what they did not know, and who built systems for finding out.
