The term “residual income” refers to the income that someone makes after their work has already been completed. An example of residual income is the earnings an author continues to make on a book after it has been published, when fans continue to purchase copies years later. Residual income is ideal because it is money that is being earned while doing nothing in the present moment to earn that money.
In equity valuation, residual income represents an economic earnings stream and valuation method for estimating the intrinsic value of a company's common stock. The residual income valuation model values a company as the sum of book value and the present value of expected future residual income. Residual income attempts to measure economic profit, which is the profit remaining after the deduction of opportunity costs for all sources of capital.