We study the optimality of taxing capital income according to a Rate-of-Return Allowance proposed by the Mirrlees Review. In a mean-variance framework the optimal tax on risk-free returns is zero with constant returns to scale in private investment, but positive with decreasing returns to scale,...

We study the optimal taxation of risk-free and excess capital income with heterogeneous rates of return, alongside an optimal nonlinear earnings tax. Households can hold three assets: one risk-free, one risky but diversifiable, and one a private investment with idiosyncratic risk whose expected...