This is the official word from the IRS.
The state of NC requires that your filing status be the same as your Federal income tax return.
Topic 353 - What is Your Filing Status?
Generally, your marital status on the last day of the year determines your status for the entire year. If you are unmarried, or if you are legally separated from your spouse under a divorce or separate maintenance decree according to your state law, and you do not qualify for another filing status, your filing status is single.
Generally, to qualify for head of household status, you must be unmarried and not entitled to file as a qualifying widow or widower with a dependent child. You must also have provided more than half the cost of maintaining as your home a household that was the main home for a qualifying person. You may also qualify for head of household status if you, though married, file a separate return, your spouse has not lived in your home during the last six months of the tax year, and you provided more than half the cost of maintaining as your home a household that was the main home for a qualifying child for more than one half of your tax year.
If you are married, you and your spouse may file a joint return or separate returns.I seperated in June and will be filing head of household this year because I've made all my own house payments and have sole custody of my children.
Hope this helps.