Which filing status applies to someone who is unmarried on the last day of the year?

The filing status of "Single" applies to an individual who is unmarried on the last day of the tax year. This means that the taxpayer does not have a spouse and has not married or filed jointly with anyone. The Single status generally results in specific tax brackets and standard deductions that are typically different from those applicable to married taxpayers. The individual must remain unmarried by December 31 to qualify for this status, which is straightforward for those without any other marital connections, such as divorce or death of a spouse during the year.

Head of household is a valid filing status but requires the taxpayer to be unmarried and provide a home for a qualifying dependent, which is not applicable if there are no such dependents. Married filing jointly and married filing separately clearly pertain to individuals who are legally married, and therefore do not apply to someone who is unmarried on the last day of the year. Thus, Single is the most accurate designation for someone in this situation.