Nonresident students, teachers, or trainees who are temporarily in the U.S. in F, J, M, or Q immigration status must file returns if they have income that is subject to withholding, even if no tax was withheld.
Nonresident aliens claiming treaty benefits must file a return.
The requirement to file a return has generally been eliminated for nonresident aliens who earn wages effectively connected with a trade or business when those wages are less than the amount of one personal exemption ($3,700 for 2011).
Even if students are exempt from filing a return, they must file Form 8843 to show their exempt status. Students and scholars who are not required to file a return should do so if they are eligible for a refund.