No - You cannot file as single. You are considered unmarried for the whole year if, on the last day of your tax year, you are either:
• Unmarried, or
• Legally separated from your spouse under a divorce or separate maintenance decree.
You are considered married for the whole year if, on the last day of your tax year, you and your spouse are married and living apart, but not legally separated under a decree of divorce or separate maintenance.
If you live apart from your spouse and meet certain tests, you may be able to file as head of household even if you aren't divorced or legally separated. If you qualify to file as head of household instead of married filing separately, your standard deduction will be higher. Also, your tax may be lower, and you may be able to claim the earned income credit. See Jerry2000's excellent explanation of the requirements for Head of Household status in his answer above.
@taxuser_3
