The Value of Tax Shields is Not Equal to the Present Value of Tax Shields : A Correction

I correct some expressions of Fernandez (2004) and provide a more general expression for the value of tax shields. This expression is the difference between the present values of two different cash flows, each with its own risk: The present value of taxes for the unlevered company and the present value of taxes for the levered company. The value of tax shields in a world with no leverage cost is the tax rate times the current debt, plus the tax rate times the present value of the net increases of debt. The value of tax shields depends only on the nature of the stochastic process of the net increase of debt; it does not depend on the nature of the stochastic process of the free cash flow