The United States has tax treaties with a number of foreign countries. Under these treaties, residents (not necessarily citizens) of foreign countries are taxed at a reduced rate, or are exempt from U.S. taxes on certain items of income they receive from sources within the United States. These reduced rates and exemptions vary among countries and specific items of income. Under these same treaties, residents or citizens of the United States are taxed at a reduced rate, or are exempt from foreign taxes, on certain items of income they receive from sources within foreign countries. Most income tax treaties contain what is known as a "saving clause" which prevents a citizen or resident of the United States from using the provisions of a tax treaty in order to avoid taxation of U.S. source income.
If the treaty does not cover a particular kind of income, or if there is no treaty between your country and the United States, you must pay tax on the income in the same way and at the same rates shown in the instructions for the applicable U.S. tax return.
Many of the individual states of the United States tax income which is sourced in their states. Therefore, you should consult the tax authorities of the state from which you derive income to find out whether any state tax applies to any of your income. Some states of the United States do not honor the provisions of tax treaties.
This page provides links to tax treaties between the United States and particular countries. For further information on tax treaties refer also to the Treasury Department's tax treaty documents page.
See Table 3 of the tax treaty tables for the general effective date of each treaty and protocol.