Are you Married for Tax Purposes?
You are married for tax purposes as of December 31. So, if you were married on or before December 31, 2013, you would be single (or head of household depending upon the circumstances for the 2012 tax year, but you would be Married for 2013. Even if you were married on December 31. 2013, you are married for the entire year.
As a married person. you may file jointly with your husband or wife, or as married filing separately.
You may not file as single or head of household.
Note, if you and your spouse are both employed, especially if your income is similar, you may end up paying more tax being married (especially if you previously filed as head of household.) This is called the “marriage penalty.”
Here is a handy marriage penalty calculator:
Marriage Tax Penalty Calculator