Managerial accounting defines residual income in a corporate setting as the amount of leftover operating profit after all costs of capital used to generate the revenues have been paid. It is also considered the company's net operating income or the amount of profit that exceed its required rate of return. Residual income is normally used to assess the performance of a capital investment, team, department or business unit.
Residual income is when you continue to get paid after the work is done. This includes royalties from books, movies, or songs and also income that comes from real estate or business investments where you don’t actually have to be present to earn it. For example, Bill Gates is still making a residual income from Microsoft even though he isn’t working there anymore.