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.
Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.