We extend the WACC approach to a tax system having a firm income tax and a personal income tax of the investor as well. We use an artificial tax system incorporating most of the G-7 national tax codes as for example the classical or the imputation systems.

We analyze a general business tax in an uncertain economy. Our tax system allows for a time-dependent tax rate and to this end we incorporate a generalized allowance for corporate equity (ACE). The generalized allowance is given by a fraction of the product of interest rate and book value of the...