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For nonresident taxpayers who meet the substantial presence test, they will attempt to meet the closer connection exception. For taxpayers who are permanent residents (and some U.S. citizens), they may want to make a return position based on the tax treaty. For example, a permanent resident may choose non-resident treatment for U.S. tax purposes - which is one of several different types of tax treaty return positions. You can read more here https://www.hg.org/legal-articles/qlarant-audits-7-keys-to-a-strong-defense-61489. Good luck!