What determines the filing status of married individuals who have been separated for some time?

The filing status of married individuals who have been separated for some time is determined by their marital status as of the end of the tax year. According to IRS guidelines, to be considered married for tax purposes, a couple must be legally married on the last day of the tax year. This means that if they are still legally married, they can file as married filing jointly or married filing separately, regardless of how long they have been separated during the year.

This understanding is crucial because it emphasizes that the tax implications rely solely on their legal status at year-end, rather than their physical separation or other factors such as whether they have children or previous filing history. This principle ensures consistency in tax treatment and aligns with how the IRS defines marital status for filing purposes.