Managerial accountants define residual income as the amount of operating revenues left over from a department or investment center after the cost of capital used to generate the revenues have been paid. In other words, it’s the net operating income of a department or investment center. You can also think of it as the amount that a department’s profits exceed its minimum required return.
What if the manager of the Idaho investment center wants to invest $100,000 in new equipment that will generate a return of $16,000 per year? This would provide residual income of $4,000, which is the amount by which it exceeds the minimum 12% rate of return threshold. This would be acceptable to management, since the focus is on generating an incremental amount of cash.
Many people talk about passive income and create the impression that you never have to do anything to keep that income going. The truth is that you will normally have to keep your eye on things if you want it to run smoothly. For example Richard Branson doesn’t run any of the 400+ companies he started but he goes over the numbers each day to make sure they’re performing well and calls the CEO if there are any problems.