Abstract This paper investigates the relationships between the profitability, rate of investment and growth rate of a business, and the cash surplus thereby produced. These relationships can be applied to a company as a whole, or to the individual businesses within that company. The basic relationships derived are financial and do not take explicit cognizance of the physical volume sold. They thus enable a business to be considered as a money-making machine, regardless of the product involved. They also do not require definition of inflation per se, although this factor will obviously have an impact on certain of the others. A company as a whole can be considered as a portfolio of separate businesses, each having a different profitability and growth rate, and each contributing a surplus or deficit to the overall cash flow. Understanding the underlying relationships for each business will facilitate portfolio planning, where the cash demands of some businesses have to be met by the surpluses provided by others.