Post- to Pre-Tax Discount Rates: Not a Simple Conversion

Abstract

Abstract It is widely accepted that financial markets tend to make assessments of value on expectations of post-tax cash flows, since that is what equity investors receive. There is however, from time to time, a need to ascertain and apply a pre-tax discount rate to discount pre-tax cashflows. Examples include (i) the assessment of regulatory returns and (ii) impairment testing of cash generating units. This paper highlights the implicit assumptions inherent in the most commonly applied shorthand method of determining pre-tax discount rates before considering modifications to create a more realistic assumption set. The paper concludes with the derivation of a shorthand formula for finite life project cashflows, which often require a pre-tax discount rate. The author agrees that while all the cash flows should be modelled on a post-tax basis and then back solved, using an iterative approach, to find the actual pre-tax rate, where a shorthand is required the formulae discussed in this paper can be applied, provided the limitations are understood.