迟来的讨论

Basically we must clear the definition of “resident” under the taxation law.
There are two ways to be a US resident under the taxation law.
1) Green Card Test
A green card allows you to live and work in the United States. If you have this status, you are considered a resident under US domestic law.

2) Substantial Presence Test
This test does not apply to green-card holders. This test measures the amount of time you spend in the United States, over a three-year period.
i) The days in the US during the current year
ii) The days in the US during the prior year x 1/3
iii) The days in the US during the second prior year x 1/6
If the total equals or exceeds 183, you meet the test and you are a "resident". If you spend over 4 months per year in the US (122 days), you will meet the test.