Taxation of nonresident aliens in the U.S.: Before understanding the taxation for nonresident aliens, we have to understand the taxation system of the U.S. as described below: Classification of U.S. people for tax purposes: All the people residing in the USA  can be classified into the following four groups for tax purposes: U.S. citizens. Permanent resident aliens (popularly called green card holders, though the card color is pink) Resident aliens. Non-resident aliens. The taxation system of the USA for resident aliens, US residents, or U.S. citizens: You must go through the US government or IRS website for full details. However, a brief idea is given here: Taxes on worldwide income. Receivable forms no.W-2 and 1099 Form number 1040 for income tax return filing. Eligibility for itemized deduction. May claim unrestricted withholding allowances. The U.S. Taxation system for nonresident aliens: The important points of the U.S. taxation system for nonresident aliens are listed b...