Many married people file their taxes as Head of Household in order to save money, not realizing that there are very strict requirments for such a status. In order for you to qualify as "considered unmarried" you must meet the following criteria taken directly from the IRS website:
To qualify for head of household status, you must be either unmarried or considered unmarried on the last day of the year. You are considered unmarried on the last day of the tax year if you meet all the following tests.
You file a separate return. A separate return includes a return claiming married filing separately, single, or head of household filing status.
You paid more than half the cost of keeping up your home for the tax year.
Your spouse didn't live in your home during the last 6 months of the tax year. Your spouse is considered to live in your home even if he or she is temporarily absent due to special circumstances. See Temporary absences , later.
Your home was the main home of your child, stepchild, or foster child for more than half the year. (See Home of qualifying person , later, for rules applying to a child's birth, death, or temporary absence during the year.)
You must be able to claim the child as a dependent. However, you meet this test if you can't claim the child as a dependent only because the noncustodial parent can claim the child using the rules described later in Children of divorced or separated parents (or parents who live apart) under Qualifying Child or in Support Test for Children of Divorced or Separated Parents (or Parents Who Live Apart) under Qualifying Relative. The general rules for claiming a child as a dependent are explained later under Dependents .