A different definition of residual income is that this is income derived from passive investments, rather than from a person's active income-generating activities. Examples are interest income, royalty income, rent, and increases in the value of investments held. Individuals typically work throughout their careers in order to build up a sufficient amount of this income to support them during their retirement.
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.