In this brief, we describe the features of the US tax system that favor buybacks over dividends. We also estimate the size of those tax advantages. In the absence of any excise taxes, we calculate the US tax advantage for buybacks over dividends would be 7.2 percent. About two-thirds of the total US tax advantage is attributable to foreign shareholders. We test the sensitivity of our estimates to various assumed parameters and estimate the range of the tax advantage at between 6 and 10 percent. Even the lower bound of this range is significantly larger than the 1 percent excise tax under current law or a 4 percent rate proposed by the Biden Administration. Our estimates are static, and we do not attempt to estimate the general equilibrium effects of a change in the buyback excise (i.e., the effects on investment and distribution after corporations and investors have adjusted to the new tax rules). Subject to these caveats, our estimates suggest that increasing the buyback excise tax could raise additional federal revenue and still leave a tax advantage for buybacks.