Most business owners don't actually know what's in their accounts payable, payroll, or inventory. Waiting for perfect data creates friction. Start working with what you have now instead of chasing idealized requirements.
95% of the time, even the business owners don't know about their business. What's happening with AP department, payroll department, how much inventory do they have, how much inventory is sitting in their Amazon. So there are things like which needs clarity over there. So obviously these assumptions would be needed. Let's start with whatever you collect. Don't stop yourself because many experts I have seen resist because the scoping document cannot be finished. So I think there is some resistance and there is some friction which we have to avoid because there is a huge gap which has been created between financial modelers and end users.