If there were children living with you in a home for which you pay more than half of the cost of upkeep and you lived apart from your husband for more than the last 6 months of the year, you can be considered unmarried for tax purposes and claim the head of household filing status. Otherwise, you must file married filing separately. See the following: Considered Unmarried 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 You paid more than half the cost of keeping up your home for the tax year. Your spouse did not 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. Your home was the main home of your child, stepchild, or foster child for more than half the year. You must be able to claim an exemption for the child. (There are some exceptions to this rule, see IRS Pub 17, Chapter 2 and 3) You can find Pub 17 at this link
http://www.irs.gov/pub/irs-pdf/p17.pdf
