Estimating Corporate Marginal Tax Rates with Asymmetric Tax Treatment of Gains and Losses.

Abstract A number of recent studies of business decision-making have used the firm's tax status as an explanatory variable, with tax status often represented as a binary variable for the existence of a net operating loss (NOL) carryforward. This paper defines corporate marginal tax rates based on the change in taxes payable as a result of earning an additional dollar of taxable income in the current period. Four scenarios are presented to illustrate this definition and to highlight the impact of both the NOL rules and future taxable incomes (TIs) on marginal tax rates. The shortcomings of the existing proxies are obvious from this analysis. A simulation procedure (generating future TI series for each firm) is outlined and illustrated on a stratified random sample of 200 firms selected from the Compustat tapes. Some sensitivity analysis is also conducted. The simulation procedure is relatively simple-to-implement for researchers requiring firm-specific estimates of corporate marginal tax rates or wanting to examine the potential effects of proposed tax law changes.