Drawing on confidential Internal Revenue Service (IRS) data, we examine whether privately held corporations are more aggressive tax planners than their publicly held peers. Contrary to conventional wisdom, we find no consistent evidence that private firms are more aggressive tax planners. We then examine whether private firms’ tax planning differs from that of public firms more generally. We find that private firms engage in more conforming tax planning (planning that also reduces pretax accounting income). However, tests of nonconforming tax planning reveal that private firms generally engage in the same or less planning relative to their public peers. Overall, our findings cast doubt on the belief that private firms are generally more aggressive tax planners than are public firms, but confirm that they engage in more of some forms of general (i.e., conforming) planning. Data Availability: The IRS provided confidential tax information to Michele S. Mullaney pursuant to an Intragovernmental Personnel Act of 1970 (IPA) agreement through the Statistics of Income (SOI) Joint Statistical Research Program (JSRP).

This paper demonstrates that the equilibrium impact of capital gains taxes reflects both the capitalization effect (i.e., capital gains taxes decrease demand) and the lock‐in effect (i.e., capital gains taxes decrease supply). Depending on time periods and stock characteristics, either effect may dominate. Using the Taxpayer Relief Act of 1997 as our event, we find evidence supporting a dominant capitalization effect in the week following news that sharply increased the probability of a reduction in the capital gains tax rate and a dominant lock‐in effect in the week after the rate reduction became effective.