26 USC 27 - Taxes of foreign countries and possessions of the United States; possession tax credit

(a) Foreign tax credit 
The amount of taxes imposed by foreign countries and possessions of the United States shall be allowed as a credit against the tax imposed by this chapter to the extent provided in section 901.

(b) Section 936 credit 
In the case of a domestic corporation, the amount provided by section 936 (relating to Puerto Rico and possession tax credit) shall be allowed as a credit against the tax imposed by this chapter.