The U.S. has one of the most complex tax systems on earth. Wealthy immigrants who want to preserve and secure their assets cannot afford to forgo careful tax planning before they arrive in America. Consulting qualified U.S. tax, financial and legal professionals should begin before starting the immigration process. It is important to understand (and often overlooked by many) that a non-resident alien (“NRA”) can become a U.S. tax resident (liable for income tax purposes) without ever being physically present in United States. Holders of a “green card” are automatically considered to be a U.S. tax resident once they are lawfully admitted for permanent U.S. residence. Resident aliens are taxed identically to U.S. citizens on their worldwide income, regardless of source. The U.S. tax system for individuals is based on a calendar year, which requires tax returns to be due by April 15th providing for extensions until October 15th. To be considered a resident alien, a person has either lawful permanent residency during any period in the tax year or has satisfied what is known as the “substantial presence test”.