We examine the effect of increased book-tax conformity on corporate capital structure. Prior studies document a decrease in the informativeness of accounting earnings for equity markets resulting from higher book-tax conformity. We argue that the decrease in earnings informativeness impacts equity holders more than debt holders because of the differences in payoff structures between debt and equity investments such that increases in book-tax conformity lead to increases in firms’ reliance on debt capital. We exploit a natural experiment in the U.S. and find that firms facing an increase in required book-tax conformity increase leverage relative to other firms. We also provide evidence of an increase in the cost of equity (but not of debt) capital for firms facing an increase in required book-tax conformity relative to control firms and that these increases in cost of equity capital are positively associated with an increase in leverage. Our findings are consistent with firms substituting away from equity and towards more debt in the presence of higher book-tax conformity.

We survey companies and find that many use incorrect tax rate inputs into important corporate decisions. Specifically, many companies use an average tax rate (the GAAP effective tax rate, ETR) to evaluate incremental decisions, rather than using the theoretically correct marginal tax rate. We find evidence consistent with behavioral biases (heuristics, salience) and managers’ educational backgrounds affecting these choices. We estimate the economic consequences of using the theoretically incorrect tax rate and find that using the ETR for capital structure decisions leads to suboptimal leverage choices and using the ETR in investment decisions makes firms less responsive to investment opportunities.