Money
Money from outside, money owed, and the clock it moves on. Each line is a kind of money event — the kind decides which of your statements move, and the line under it says which.
What customers owe you is in the model: each way you make money says when its money actually arrives, and a share never paid is counted as lost. So the cash curve follows the money arriving, not the sale. What you owe is in the model once you say when you pay your suppliers; blank means every cost is paid the month it happens. Money from outside is entered here — a loan, an investment or a grant each move the model differently, and that difference is the point. Tax is yours to state. Still honestly absent: equipment and other things you buy to keep — nothing here buys a machine, spreads its cost over years or sells it.