Hi, I'm a Canadian working in the US with a TN. My wife quit her job in the mid year and came lived with me with TD. She does not have a tax idenfication number. I've read somewhere (maybe this site?) that I can still file jointly (for US federal) because of the US-Canada treaty. Is that correct? Also, I want to file using the 1040NR. Do I need to file any extra forms like a 8840? Or is that all covered by the US-Canada treaty.

I know I'm really late, but hope this is an easy question?

Thanks a bunch!

If you file jointly, it will be as a resident alien. Based on what you have provided, that is NOT an option.

You CAN, however, claim your wife as a dependent.