If a married nonresident alien’s spouse is not a U.S. citizen, which filing status must they use for tax calculations?

A married nonresident alien whose spouse is not a U.S. citizen is required to use the filing status of married, filing separately. This is primarily because, as a nonresident alien, the individual does not have the option to file jointly with a nonresident spouse. The tax regulations typically allow nonresident aliens to only file as married filing separately unless both spouses elect to be treated as resident aliens for tax purposes, which involves specific criteria and considerations. This filing status also reflects the realities of their circumstances and ensures compliance with IRS requirements.

Other filing statuses, such as head of household or single, would not be applicable because they don't accurately represent the taxpayer's marital situation. The head of household status requires that the individual maintain a household for a qualifying person and be considered unmarried, neither of which applies here. Similarly, the single status cannot be claimed by a married individual. Therefore, using married, filing separately aligns with their situation and adheres to IRS rules for nonresident aliens.