The paper analyses optimal taxation of corporate profits when governments c
an choose both the rate and the base of the corporation tax, but are constr
ained to collect a given amount of corporate tax revenue. In a standard two
-period model of investment and international mobility of portfolio capital
only, the optimal tax system allows a full deduction for the costs of capi
tal. When foreign direct investment is permitted, however, and firms can sh
ift profits between countries through transfer pricing, it will be optimal
for each government to distort investment decisions in order to reduce tax
rates and limit the incentive for profit shifting.