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In this paper, I investigate how to tax the different sources of income of taxpayers. I consider on optimal nonlinear income tax model with many sources of income. I first exhibit a specification where the optimal tax system consists in a nonlinear schedule that applies to the sum of all income - a comprehensive income tax system - and another specification where the optimal tax system consists in a nonlinear schedule specific to each income - a separate income tax system. In the more general environment I specialize the tax schedule to be combination of these two polar systems: the tax system is restricted to be the sum of a comprehensive personal income tax schedule and of income specific tax schedules, I derive an optimal ABC formula for each of these schedules. I also derive a condition expressed in terms of empirically meaningful sufficient statistics under which decreasing the indexation of the personal income tax base on one income and compensating the revenue loss with a lump-sum or a proportional increase in the taxation of that income is socially desirable
