The United States charges income tax on all U.S. citizens and permanent residents based on worldwide income. Treaties and various exemptions eliminate some but not all of the risk of double taxation. Each state of the United States has its own tax system. Investors should consider the tax effects of becoming a U.S. resident before investing. As a general rule, if you are moving all of your assets to the U.S. you will not have a problem with double taxation. If you will continue working or investing in your home country after moving to the U.S., a trip to your tax advisor is in order.