what is irs publication 519 
irs publication 519 is the u s tax guide for aliens a document the internal revenue service irs publishes that details the tax procedures for aliens individuals that are not citizens of the united states 1 not all aliens are subject to u s taxes resident aliens those who have been in the country for a defined period are subject to taxation on their worldwide income just as citizens are non resident aliens are only taxed on income they earn within the u s as well as on certain types of international income 2 understanding irs publication 519the most important aspect of irs publication 519 is its definition of a taxpayer s status as either a non resident alien or a resident alien using the substantial presence test or the green card test as the applicable tax rules are based on that status taxpayers may also be considered as dual status aliens and should also determine the tax status of any spouse 3 the substantial presence test measures residency by physical presence in the u s to meet this test an individual must reside in the u s on at least the green card test states that an individual is a resident for u s federal tax purposes if they are a lawful permanent resident of the u s at any time during the calendar year a person becomes a lawful permanent resident if they have been given the privilege according to the immigration laws of residing permanently in the u s as an immigrant generally by being issued an alien registration card also known as a green card by the u s citizenship and immigration services 5 if an individual qualifies as both resident and non resident in the same year they have what is referred to as dual status a married individual may also have a choice of treating their non resident spouse as a resident alien 6 taxation of non resident incomeindividuals determined to be non resident aliens are generally subject to two different tax rates on their u s income one for effectively connected income and one for fixed or determinable annual or periodic fdap income effectively connected income is earned from running a u s business or performing personal services and is taxed at the same graduated rates as a u s citizen fdap is considered passive income and is taxed at a flat 30 rate 7 non resident aliens must file tax returns using form 1040nr 8 for non resident aliens tax treaties with foreign countries may reduce or eliminate u s tax on various types of personal services and other income such as pensions interest dividends royalties and capital gains 9 