This paper studies the implications of monopsony power for optimal income taxation and welfare. Firms observe workers’ abilities while the government does not and monopsony power determines what share of the labor market surplus is translated into profits. Monopsony power increases the tax incidence that falls on firms. This makes labor income taxes less (more) effective in redistributing labor income (profits). The optimal tax schedule is less progressive. Monopsony power alleviates the equity-efficiency trade-off that occurs because the government does not observe ability, but at the expense of exacerbating capital income inequality. I illustrate these findings for the US economy.
JEL classification: H21, H22, J42, J48
Keywords: monopsony, optimal taxation, tax incidence