TN & Taxes ?!?

Also, wouldn't the tax treaty between the States and Canada prevent double taxation? Isn't that what it's there for ?!?

man... this is all very complicated. I've been in the US on a TN for the past few years. I have been filing taxes in the US since I started college in the US like 9 yrs ago. I went from a F-1 to an OPT to a TN. I normally visit home (Canada), about twice a year. I am only filing for US taxes. Should I be doing anything different?

Well if you've already moved your tax home to the US it's too late now, but on F-1 you should keep your tax home in Canada and on TN-1 it can also be a good idea depending on how long you're staying.

But if you've been filing 1040s for years now then just keep on doing it like any US resident does, the only thing to bear in mind really is to sever all residential ties to Canada (otherwise the CRA can deem you resident) and if you ever move back to Canada (or get refused entry) that there is a lot of paperwork to file to move your tax home back to Canada. Read IRS publication 519.

Also notify the CRA that you are no longer resident in Canada if you haven't already.

The only problem really is that it can be a bit dicey on TN-1 because the law says your stay must be "temporary". I've had a bit of a discussion with the IRS about this subject and they ended up saying they're going to have to talk to their lawyers about it.