Matthew Klein discusses corporate and personal income tax evasion and avoidance in the FT (part 1, part 2), with reference to a JEP article by Gabriel Zucman. Klein makes several points:

• Profit taxes were introduced as complements to income taxes, in order to make it more difficult to evade taxes by routing profits through fabricated corporate structures rather than distributing them. To avoid double taxation, capital gains and dividends typically are taxed at lower rates than labor income.
• Whether corporate taxation should be coordinated internationally is not a new question. The League of Nations already debated it. The issue regained importance as international trade and cross-border profit flows rose.
• Today, a third of US corporate profits are generated outside of the US. Of those, more than half are generated in Ireland, Luxembourg, the Netherlands, Singapore, Switzerland and the Carribean. Both shares have increased over recent decades (see the figure below which is taken from Zucman’s article). This might have contributed towards lowering the effective corporate tax rate of US corporations in the US.
  
• If the objective is to (i) avoid double taxation and (ii) render cross-border profit shifting irrelevant, an easy way forward could be to credit a corporation’s taxes paid worldwide against the personal income taxes owed by the corporations shareholders. This would imply that higher corporate taxes abroad could lead to lower domestic income tax revenue, a difficult political sell. It would also imply that unrealised capital gains may go untaxed.
• Based on discrepancies between national balance of payments statistics, Zucman estimates that 8% of global household financial wealth is not reported to tax authorities (see the table below which is taken from Zucman’s article).
  
• He proposes to impose high tariffs on exports originating from “tax havens” to force these countries to exchange information about bank accounts and, in the medium term, to create an “international financial registry.”