中國和美國之間簽有稅收協定，對于學生和教師有一定數額的稅務減免。當然還有其他職業也有減免，不過我們最常見的是持F1/J1簽證來美國的學生和學者。剛好有一位讀者提到她是從法國來美國讀博后，那么中國公民從第三國來美國，還能否使用中美 treaty 呢。我不是專業稅務員，只是從中美協定談一下我的理解。
中國公民在中國申請F1/J1簽證來美，是可以使用中美協定減稅的，詳細可讀這篇中國留學生和訪問學者在美國享受稅務減免的政策。但從第三國申請來美，應使用中美協定還是第三國和美國的協定，就比較頭疼。一般有兩種理解：
1.只要是中國公民，就應該用中美協定。
2.在第三國生活了一定時間，已成為該國的 tax resident，應使用該國和美國的協定。
目前，IRS 是按照第二種理解來處理的。很多人的經驗也是從第三國申請來美，學校不按中美 treaty 操作。中美協定（原文在此）：
ARTICLE 19
(Teachers, Professors and Researchers)
An individual who is, or immediately before visiting a Contracting State was, a resident of the other Contracting State and is temporarily present in the first-mentioned Contracting State for the primary purpose of teaching, giving lectures or conducting research at a university, college, school or other accredited educational institution or scientific research institution in the first mentioned Contracting State shall be exempt from tax in the first mentioned Contracting State for a period not exceeding three years in the aggregate in respect of remuneration for such teaching, lectures or research.
ARTICLE 20
(Students and Trainees)
A student, business apprentice or trainee who is, or was immediately before visiting a Contracting State, a resident of the other Contracting State and who is present in the first- mentioned Contracting State solely for the purpose of his education, training or obtaining special technical experience shall be exempt from tax in that Contracting State with respect to:
1.payments received from abroad for the purpose of his maintenance, education, study, research or training;
2.grants or awards from a government, scientific, educational or other tax-exempt organization; and
3.income from personal services performed in that Contracting State in an amount not in excess of 5,000 United States dollars or its equivalent in Chinese yuan for any taxable year. The benefits provided under this Article shall extend only for such period of time as is reasonably necessary to complete the education or training.
因為讀者提到了法國，我又去看了一下法國-美國稅收協定（原文在此）：
ARTICLE 20
Teachers and Researchers
1.An individual who is a resident of a Contracting State immediately before his visit to the other Contracting State and who, at the invitation of the Government of that other State or of a university or other recognized educational or research institution situated in that other State, visits that other State for the primary purpose of teaching or engaging in research, or both, at a university or other recognized educational or research institution shall be taxable only in the first mentioned State on his income from personal services for such teaching or research for a period not exceeding 2 years from the date of his arrival in the other State. An individual shall be entitled to the benefits of this paragraph only once.
2.The provisions of paragraph 1 shall not apply to income from research if such research is undertaken not in the public interest but primarily for the private benefit of a specific person or persons.
ARTICLE 21
Students and Trainees
1. (a) An individual who is a resident of a Contracting State immediately before his visit to the other Contracting State and who is temporarily present in the other Contracting State for the primary purpose of:
(i) studying at a university or other recognized educational institution in that other Contracting State;
(ii) securing training required to qualify him to practice a profession or professional specialty; or
(iii) studying or doing research as a recipient of a grant, allowance, or award from a not-for-profit governmental, religious, charitable, scientific, artistic, cultural, or educational organization, shall be exempt from tax in that other State with respect to amounts referred to in subparagraph (b).
(b) The amounts referred to in subparagraph (a) are:
(i) gifts from abroad for the purposes of his maintenance, education, study, research, or training;
(ii) a grant, allowance, or award described in subparagraph (a) (iii); and
(iii) income from personal services performed in the other Contracting State in an amount not in excess of 5,000 United States dollars or its equivalent in French francs for any taxable period.
(c) The benefits of this paragraph shall only extend for such period of time as may be reasonably or customarily required to effectuate the purpose of the visit, but in no event shall any individual have the benefits of this Article and Article 20 (Teachers and Researchers) for more than a total of five taxable periods.
(d) The provisions of subparagraph (a) shall not apply to income from research if such research is undertaken not in the public interest but primarily for the private benefit of a specific person or persons.
2. An individual who is a resident of a Contracting State immediately before his visit to the other Contracting State, and who is temporarily present in that other State as an employee of, or under contract with, a resident of the first-mentioned State for the primary purpose of:
(a) acquiring technical, professional, or business experience from a person other than that resident of the first-mentioned State, or
(b) studying at a university or other recognized educational institution in the other State, shall be exempt from tax by that other State for a period of 12 consecutive months with respect to his income from personal services in an aggregate amount not in excess of 8,000 United States dollars or its equivalent in French francs.
關于 resident 的定義，中美協定第四點提到：
ARTICLE 4
(Residence)
For the purposes of this Agreement, the term "resident of a Contracting State" means any person who, under the laws of that Contracting State, is liable to tax therein by reason of his domicile, residence, place of head office, place of incorporation or any other criterion of a similar nature.
法美協議也有類似的定義。所以，該個人在和美國簽協議的國家（如中國、法國、德國、日本等）有納稅義務（liable to tax），就可叫做 resident，居民。Immediately 則指的是在入美國國境之前那一刻。協定既然用了 resident 而不是 citizen，我們應該理解成該個人在入境前那一刻是該國的居民，那么就適用于該國和美國的稅務協定，而并非單純由國籍決定。IRS 這個網頁有各國和美國的 income tax treaty 可供查看。
