Barbados

As typing in to Google "Barbados offshore" found most results in a "bank" added to the previous quote,  I can certainly say that Barbados is mostly used for offshore banking. Barbados is the 51st richest country in the world looking at the GDP per capita. With a very well developed and mixed economic system.

Double taxation treaty

Double taxation treaty is a treaty between two countries that allows the taxes to be paid in one of the involved countries. Sometimes called Double Tax Avoidance Agreement, this title is a better representation of the treaty, because the treaties are for tax double tax avoidance, not for double tax enforcement.