Contents Introduction  ........................................ 1 Important Changes   ............................ 1 Important Reminders  ......................... 3 1. Nonresident Alien or Resident Alien?  ........................................... 3 2. Source of Income  ......................... 10 3. Exclusions From Gross Income  . 13 4. How Income of Aliens Is Taxed   . 15 5. Figuring Your Tax  ........................ 20 6. Dual-Status Tax Year  ................... 25 7. What, When, and Where To File  . 33 8. Paying Tax Through Withholding or Estimated Tax  ......................... 34 9. Tax Treaty Benefits  ...................... 41 10. Employees of Foreign Governments and International Organizations  .............................. 42 11. Departing Aliens and the Sailing or Departure Permit   .................... 44 12. How To Get More Information  .... 46 Appendix A—Tax Treaty Exemption Procedure for Students  .............. 47 Appendix B—Tax Treaty Exemption Procedure for Teachers and Researchers  ................................. 49 Index  .................................................... 52 Introduction For tax purposes, an alien is an individual who is not a U.S. citizen. Aliens are classified as   nonresident   aliens   and   resident   aliens. This publication will help you determine your status and give you information you will need to file your U.S. tax return. Resident aliens generally  are  taxed  on  their  worldwide  in- come, the same as U.S. citizens.    Nonresi- dent aliens are taxed only on their income from sources within the United States and on certain income connected with the conduct of a trade or business in the United States. Table A, What You Need To Know About U.S. Taxes,  provides a list of questions and the  chapter  or  chapters  in  this  publication where you will find the related discussion. The information in this publication is not as comprehensive for resident aliens as it is for  nonresident  aliens.  Resident  aliens  are generally treated the same as U.S. citizens and can find more information in other IRS publications. Important Changes Child tax credit. In 1999, you may be able to take a credit on your tax return of up to $500 for each qualifying child. For more in- formation, see Tax Credits and Payments, in chapter 5. Department of the Treasury Internal Revenue Service Publication 519 Cat. No. 15023T U.S. Tax Guide for Aliens For use in preparing 1999  Returns