추가적으로, IRS Publication 519 – US Tax Guide for Aliens 를 참고하세요.
Substantial Presence Test
You will be considered a U.S. resident for tax purposes if you meet the substantial presence test for the calendar year. To meet this test, you must be physically present in the United States on at least:
31 days during the current year, and
183 days during the 3-year period that includes the current year and the 2 years immediately before that, counting:
All the days you were present in the current year, and
⅓ of the days you were present in the first year before the current year, and
⅙ of the days you were present in the second year before the current year.
엔지니어님께서 말씀하신 case나, 그리고 질문하신 분도 아마 그러셨을것 같은데 Substantial Presence Test 를 만족했기때문에 residency 로 취급(Form 1040)을 받았을 것입니다.