Many countries have tax treaties with the U.S. that allow their residents to earn income without being subject to income tax on those earnings in both countries.
Treaty benefits are tied to the residency of an individual immediately before entering the U.S.
Pay of professors and teachers may be exempt from U.S. income taxes for either two or three years if they are temporarily in the U.S. to teach or do research.
Students and trainees from many countries are allowed to earn tax-free income in the U.S from the college or university they attend.
Many treaties only allow students and scholars to engage in employment that is related to the reason they were admitted to the country.
Canada, India, and China have uncommon provisions for students and scholars. For more information regarding the benefits of a particular country's tax treaty, see Publication 901, U.S. Tax Treaties.