What is the filing status for Sean and Cynthia as they divorced on September 21, 2011?

The filing status for Sean and Cynthia is Single because they divorced on September 21, 2011. For tax purposes, a couple is considered married for the entire year in which they get married or for that year in which they are still married until the date of divorce. Since their divorce occurred on September 21, 2011, they would not be able to file as Married Filing Jointly or Married Filing Separately for the 2011 tax year.

After the divorce, both Sean and Cynthia would individually file as Single if they had not remarried by the end of the tax year. The Head of Household status generally applies if a taxpayer is unmarried, has a qualifying dependent, and pays more than half the cost of maintaining a home for that dependent, which isn't applicable here since there was no mention of dependents or household expenses. Thus, the most appropriate filing status for Sean and Cynthia for the year after their divorce is Single.