Ruback (1986) has shown that the one-period analysis of the present value of a riskless after-tax cash flow can be extended
to multiple periods, and streams of riskless cash flows. Before and after-tax riskless discount rates will be a function of the term structure of riskless interest rates. If individual investors calculate the present value of a multiperiod riskless after-tax cash flow using an after-tax riskless discount rate, then, again, the corporation that does not want to accept projects which some of its shareholders would prefer be rejected, and wants to make investment decisions independently of borrowing/dividend policy, has no choice but to discount after-tax riskless cash flows using a before-tax riskless
discount rate.
This can be illustrated by considering a situation with a corporate after-tax cash
flow Xð1 2 tcÞ occurring after n periods. Assuming a flat term structure of riskless
interest rates, and repayment on maturity of accumulated interest and principal of
riskless borrowing, the present values corresponding to W2 and W3 would be: