Residual income models of equity value have become widely recognized tools in both investment practice and research. Conceptually, residual income is net income less a charge (deduction) for common shareholders’ opportunity cost in generating net income. It is the residual or remaining income after considering the costs of all of a company’s capital. The appeal of residual income models stems from a shortcoming of traditional accounting. Specifically, although a company’s income statement includes a charge for the cost of debt capital in the form of interest expense, it does not include a charge for the cost of equity capital. A company can have positive net income but may still not be adding value for shareholders if it does not earn more than its cost of equity capital. Residual income models explicitly recognize the costs of all the capital used in generating income.

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The vast majority of my investing is in retirement accounts and won't be tapped for income until I reach at least 59.5 years old. However, I have a very small taxable investing portfolio (less than $5k) with Ally Invest where I invest in a handful of stocks that I value. I do not use the earnings as income – I simply hold these stocks. But I have an unrealized gain of $340 from this year so far.
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.