I started off doing short trips providing professional services for my CDN employer on behalf of my TN US employers. I spent half the year in Canada and half in the US. I was told at the time that I did not have to file US taxes because I was considered a Canadian resident temporarily assigned abroad.
Fast forward a few years and I start a 6 mo contract for a new US employer. This is still considered temporary assignment abroad. So, I filed my CDN taxes the same way I had in the past. Because my salary was in CDN and the per diem was not given to me as taxable income by my CDN employer, I didn't see how I could file anything in the US. As far as I was concerned, I was still still on a temporary assignment. I filed in Canada only. When the contract was renewed for 6 mos, and then again later for 1 yr. I stayed the course.
I thought I was doing this all correctly, but my recent research is telling me I have this all wrong. The work was performed in the US. I spent most of the year in the US. I did not get an SSN. No withholding was performed by the US employer since they had a corp to corp relationship with the CDN employer. I was paid a non-taxed per diem for my expenses because each stint was less than a year. It's been 4 years now.
Looking back now, I think I was supposed to file 1040NR in the US and use foreign tax credits on my CDN tax filing. Catching up on the US taxes might be prohibitively expensive now and I am not sure I can do anything to amend the CDN taxes to redistribute the taxes I paid to Canada to the US where it should have gone originally.
Can I apply for a SSN, file my back US taxes, refile my CDN taxes with foreign tax credits and get the money I paid Canada to the US? Am I totally SOL with this? If I get an SSN, can I start doing the right thing going forward without having this huge mess catch up with me? Like I said earlier, after years with a CDN employer, I am thinking of working for the US employer directly for a while before going back to Canada. Can I make a fresh start?
I still have property, bank accounts, RRSPs, and other assets in Canada to return to one day. And just to make it more complicated, I have a US citizen spouse, who I married 2 years ago, and who I plan to sponsor for PR to Canada while we are in the US.


