See for reference - http://www.irs.gov/businesses/small/international/article/0,,id=96314,00.html You are a resident, for tax purposes, if you are a Lawful Permanent Resident of the United States at any time during the calendar year
. This is known as the "green card" test. You are a Lawful Permanent Resident of the United States, at any time, if you have been given the privilege, according to the immigration laws, of residing permanently in the United States as an immigrant.
From immigration purposes - you generally will loose your a Lawful Permanent Resident status after one year of absence. However, you may be outside the US for two years if you get a re-entry permit from immigration authorities before leaving the US.
For tax purposes - if you are either a resident or a nonresident alien
departing the United States, you will usually have to show that you have complied with the U.S. income tax laws
before departing from the United States. You do this by obtaining a tax clearance document, commonly called a "Departure Permit" or "Sailing Permit" from the IRS
As a resident alien and if you did not have taxable income for the prior year and do not have taxable income for the tax year up to and including the date of departure, or you are a resident alien who is leaving only temporarily, use Form 2063
to apply for a departure permit. Resident aliens who have taxable income may still use Form
2063 to apply for a departure permit if the IRS is satisfied that your departure will not hinder the collection
of tax. If you are a resident alien leaving the United States with no definite plans to return for the year, you will have to complete Form 1040-C
, and pay your tax liability
as shown on the Form 1040
-C in order to get a departure permit. In certain cases, you may furnish a bond guaranteeing payment of tax, but you must pay your tax liability
when your final income tax return is due. Any tax you pay counts as a payment on your final return that you must file after the end of your tax year.
In additional - depending on your circumstances - you might be a subject of the expatriation tax
provisions - see more information in this IRS article - http://www.irs.gov/businesses/small/international/article/0,,id=97245,00.html
While it is your decision to give up your Lawful Permanent Resident status - I do not think that will provide you any tax saving. Even you are required to report all your worldwide income to the IRS - because tax rates
in the US are generally lower - using the foreign tax credit will likely eliminate your US tax liability.