Presumptive income taxes in the form of a tax on turnover for SMEs are pervasive as a way to
reduce the costs of compliance and administration. We analyze a model where entrepreneurs
allocate labor to the formal and informal sectors. Formal sector income is subjected either to a
corporate income tax or a tax on turnover, depending on whether their turnover exceeds a
threshold. We characterize the private sector equilibrium for any given configuration of tax
policy parameters (corporate income tax rate, turnover tax rate, and threshold). Given private
behavior, social welfare is optimized. We interpret the first-order conditions for welfare
maximization to identify the key margins and then simulate a calibrated version of the model.