How Does Removing the Tax Benefits of Debt Affect Firms? Evidence from the 2017 US Tax Reform

Despite extensive efforts, the relation between tax incentives and corporate capital structure is an open question. The 2017 US tax reform creates an opportunity to directly estimate this relation. The reform limits the tax advantage of debt for all firms except for small businesses with average sales below $25 million. I use the exception threshold in a regression discontinuity design and show that corporate debt declines nearly dollar for dollar as the present value of the tax benefits of debt shrinks. Treated firms do not raise equity to replace debt, and they decrease investments and hiring, consistent with a rise in the cost of external financing. Confirming the tax channel, treatment effects are stronger in firms with more profits and smaller non-debt tax shields. Comparing the size of the debt tax shield across the firm size distribution suggests that the estimates likely provide a lower bound for the effects in large corporations