This paper demonstrates that, contrary to previous analyses, if investors calculate the
present value of a riskless after-tax cash flow by discounting with the after-tax riskless
interest rate, and if different investors have different marginal tax rates, then a
corporation that does not want to accept projects that some of its shareholders would
want rejected, wants to use an accept/reject investment criterion independently of its
borrowing/dividend policy and does not know the marginal tax rates of its
shareholders, cannot use an after (corporate) tax discount rate instead of a before-tax
discount rate to calculate the “present value” of riskless after-tax cash flows.
Managerial decision-making investment rules are thus clearcut and there is no need for
rules of thumb such as “be consistent, discount after-tax cash flows with an after-tax
discount rate”.