Proving U.S. Citizenship

• A nonresident alien who wants to pay resident tax has to prove his citizenship by first passing the green card test. The IRS says that all this requires is being able to prove that a nonresident was a permanent resident of the United States for at least one calendar year. But a nonresident also has to pass the substantial presence test, which goes into more detail of where he lives in the U.S. A nonresident will have to prove that he lived in one of the 50 states or the District of Columbia. In addition, he must prove he was on the mainland at least 31 days out of a year and lived in the U.S. at least 183 days out of a three-year period.
  
  

Form 1040NR

• A nonresident living in the U.S. and earning income will have to fill out either IRS Form 1040NR or 1040NREZ (see Resources). On the regular 1040NR form, a nonresident has to first indicate his personal information and show what country he's from for his filing status. He then has to list his exemptions and income effectively connected with a U.S. business. Next, he figures gross income, tax and credits, any miscellaneous taxes, payment or refunds. The Schedule A section will require him to list any itemized deductions, and the Schedule NEC section requires him to list taxed income not made in the United States. Finally, Section OI (Other Information) will ask a nonresident to answer various questions about his citizenship.
  
  

Form 1040NR-EZ

• This much easier income tax form is only for nonresidents with no dependents. On it, a nonresident first has to give his personal information and indicate whether he's a single nonresident alien or married. Then he can list all of his earnings, deductions or tax withheld in one convenient box. He may have to attach a W-2 or 1042-S form with this form and a 1099-R if his income tax was withheld (see Resources). Finally, he simply needs to list his refunds, plus answer questions about his citizenship in Section OI at the end.
  
  

Filing as a Nonresident

• If a nonresident has income tax withholding, he has to file his taxes by April 15 as regular U.S. residents do. Taxes by a nonresident that are not withheld are filed at a considerably different date from regular residents. In this scenario, the nonresident has until June 15 to file.
  
  

Resident Taxes

• All legal residents of the United States have to file taxes normally with a 1040, a 1040A or 1040EZ form by April 15. The IRS reminds that full residents of the U.S. will also be taxed on any income made in a foreign country. The TurboTax website says that residents who live in one state and work in another have to file a separate return from the state they work in as a different definition for nonresident tax. Residents can commonly take credits for working in another state so they are not double-taxed.