As junkseller states, for federal purposes, you file married filing jointly. For the state return, it depends on the state you live in and whether or not your state recognizes same sex marriages or if it even matters at all. From junkseller, it appears that NC does not recognize same sex marriage and you and your partner will have to file separate returns. For PA it doesn't really matter, everyone's taxes are essentially calculated as if they were single with no kids (for low income taxpayers, dependents can increase tax forgiveness lowering your income tax). There really is little or no advantage for filing married in PA. For my wife and I it doesn't really matter if we file separate or together, our tax liability is the same.
Couple things to note about your federal tax return. Even though you were not married until 12/27/2013, the federal tax code sees you as married for the entire year. Since you are legally married and recognized by the federal government, you and your spouse only have 2 options for filing your tax return: married filing jointly or married filing separate (This is NOT the same as filing single. MFS is one of the worst ways to file unless you absolutely have to). You can no longer file as single or head of household (whether or not these filing statuses would result in a combined lower tax bill for you and your spouse). Like many married couples filing jointly for the first time, particularly if they both have incomes, the income tax on the joint return may be higher than the income tax if you each filed single (but, filing single is no longer an option).
Your tax return could be even more complicated (at least next year) if you lived in Washington state or Colorado and ran a legal recreational marijuana business. Your business is legal according state laws but illegal according to federal laws. If you report your income from the business to the IRS, you acknowledge you are earning income from an "illegal" activity. If you don't report your business income, it is tax fraud for failing to report all of your income. Damned if you do and damned if you don't.
I think the tax laws should be simplified. Everyone should file single, personal relationships are none of the IRS' business. Report all income, I don't see it as the IRS' job to determine what is or is not a legal business. That is the job of law enforcement, not the IRS.
