The Green Card Test (GCT) is a criterion used by the Internal Revenue Service (IRS) in the United States to determine whether an individual qualifies as a "resident for tax purposes".
The GCT asks whether, during the calendar year, an individual spent at least one day in the US as a lawful permanent resident (i.e. possessed a green card).
There exists an exception to the Green Card Test if an individual stops being a lawful permanent resident during the calendar year.
[3] Passing the Green Card Test guarantees that an individual will be treated as a "resident for tax purposes" for the entire year.
However, a withholding agent must wait until receiving an official document from the Immigration and Naturalization Service to treat the individual as a "resident for tax purposes".