U.S. Tax Residency Status As a general matter, all U.S. citizens and U.S. residents are treated as U.S. tax residents. A non-U.S. citizen is generally classified as a nonresident for U.S. tax purposes unless they satisfy one of two tests: the green card test or the substantial presence test. The U.S. residence tests are generally applied on an annual calendar-year basis. International Tax Concepts: Tax Residency Status