[occamrazor]

Basically, you do not consider payment to non-cooperating countries for tax purposes.

For example ACME Inc. produces widgets with costs of 50 and revenue of 100 in the US. To avoid taxes, it also pays 50 in "licensing fees" to ACME Tax Heaven in the Cayman Islands, so that the profit in the US is 0.

If the payment to the Cayman Islands is not counted, then the taxable profit in the US becomes 50.