If you were a nonresident alien and were present in the United States during any part of the tax (calendar) year in question on an F,J, M, or Q visa, there is at least one tax form you must complete (IRS Form 8843).
If you were a nonresident alien who did not receive funding from a U.S. source (please be aware that funding from a foreign source that is paid through Harvard is usually considered U.S.-source), you do not have to complete an actual tax return (eg.1040 NR), but, as mentioned above, may...
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