I am in a Common Law Partnership in Canada (considered a de facto relationship in Canada) , for US tax purposes am I to file as married or single?

[Carl]

Are you a U.S. Citizen? Is your spouse? Generally speaking, if the local laws of wherever you may be recognize your status as "married", and you meet all the requirements as it pertains to those local laws, then for U.S. tax purposes you are married. But I can't know that for sure if you or your spouse are not a U.S. Citizen.

I do know that both of you would need to have either an SSN or an ITIN.

[ericherie]

I am a US citizen, but my common law partner is not.  In Canada, 'Living Common Law' is a situation which a couple lives together for one year but are not recognized as married, but for Canadian tax purposes state we are 'living common law spouses/partners'.

I'm not sure if the situation meets the US common law marriage situation, or simply a registered domestic situation.