第一种情况，F2在美逗留不足2个月，转成F1（不论是否回国签证），可以享受Treaty
，可以找payroll office递交8233免除tax withholding。
第二种情况，F2在美逗留超过2个月，转成F2。这个定义比较模糊，主要因为Tax
treaty中没有对residency作明确的定义。对于在美国换签证的，P4152明确说明要在
home country逗留365天才可以；对于回国换签证的，我没找到明文规定. Revenue
Ruling 56-164 和 General Counsel Memorandum 37047, 好像有相关说明，我不是很
确定。但是在中国的 “国际收支统计申报办法 PROCEDURES GOVERNING THE
DECLARATION AND STATISTICS ON INTERNATIONAL RECEIPTS AND PAYMENTS”，Article
3 The term ``Chinese residents'' as referred to in these Procedures
includes：
（1） all natural persons who have resided within China over one year
except students and patients from foreign countries or from the regions of
Hong Kong， Macau and Taiwan and foreign staff of foreign embassies or
consulates in China and their families；
（2） Chinese citizens staying abroad for a short duration （less than one
year）， Chinese students studying abroad， Chinese patients seeking
medical treatment abroad and staff of Chinese embassies or consulates and
their families；
（1）说似乎只要在中国呆够一年以上都可以作为residnct；
（2）特别强调Chinese students studying abroad 算是resident
考虑到tax treaty应该简历在mutual respect的基础上，是否是中国居民应该由中国税
发来限定。这样的话，其实无论在哪里换签证都应该可以使用treaty（可是鉴于p4152
明问规定，在美国换签的希望不大）。
最后一种情况J1／J2－》F1，由于J1已经使用过article（19），不满一年就无法使用
article（20）了，详细见irs nr specialist 的解释：
The IRS Requirement to Reestablish Treaty Country Residence
Between Treaty Claims
By Lowell G. Hancock, IRS NRA Tax Specialist
In 1998 the IRS published Field Service Advice 1998-61, in which it took the
position that, unless the treaty language specifically provides otherwise,
a student who changes status to a teacher/researcher without leaving the USA
is not entitled to the tax treaty's exemption for teacher/researcher wages
unless the alien involved first leaves the USA for a period of at least 12
months, and then re-enters the USA as a teacher/researcher. The IRS also
holds to the position that, unless the treaty language specifically provides
otherwise, a teacher/researcher who changes status to a student without
leaving the USA is not entitled to the tax treaty's exemption for student
wages unless the alien involved first leaves the USA for a period of at
least 12 months, and then re-enters the USA as a student.
Example: Peoples’ Republic of China Tax Treaty
Article 19 (Professors, Teachers and Researchers) and
Article 20 (Students and Trainees)
The language of the USA-China treaty does not allow a student who changes
status to a teacher/researcher to claim the benefit of the teacher/
researcher article without first leaving the USA for a continuous period of
12 months, and then re-entering the USA as a teacher/researcher.
Similarly, the USA-China treaty does not allow a teacher/researcher who
changes status to a student to claim the benefit of the student article
without first leaving the USA for a continuous period of 12 months, and then
re-entering the USA as a student. The 12-month period for re-establishing
residency in the home country does not arise from the language of any treaty
. Rather, it is found in Revenue Ruling 56-164 and in General Counsel
Memorandum 37047, which provide information on how the IRS interprets
certain aspects of the tax treaties.
