Posted: Mon Jul 21, 2008 10:45 am-
http://www.cra-arc.gc.ca/E/pub/tg/p151/README.html (File Form 8891 for the RRSP if you move your tax home to the US).
The short answer is yes, it can affect your TN renewal if they start grilling you. To get TN-1 you have to have "bona-fide non-immigrant intent" and if you are declaring to the IRS that you are a resident by filing a 1040 instead of a 1040NR and you are declaring to the CRA that you are non-resident and have cut all residential ties, clearly you are violating that rule.
Having said that, the question may not come up.
Going by the threads on here the general impression I get is that moving your tax home to the US is a bad idea unless you are sure you are aware of the implications of doing so (and they are many and various), because moving it temporarily to the US can cause you all sorts of headaches not related to the TN-1.
Generally, only do it if you save enough tax money to hire a good cross-border accountant in Canada who is fully aware of all the forms. Emphasis on the "good". Find one before you go, I would suggest. I've used Serbinski and he is near you.
One of the various problems for example is that if you get refused entry and you have moved your tax home to the US, you essentially become a resident of Canada again at that point which means a ton of tax paperwork you weren't expecting.
You should read IRS publication 519.
What the IRS doesn't make terribly clear in that document and the CRA doesn't make terribly clear in the above document is that you can remain a tax resident of Canada pretty much forever if you are in a temporary status in the US, by filing Form 1040NR and making a tax treaty claim on Form 8833. This means you can carry on contributing to your RRSP for example.
However publication 519 does explain how to move your tax home to the US, i.e. filing a dual-status return if you move mid-year (this means three tax returns in the year that you move, a T1, a 1040 and a 1040NR). Just be aware that moving it back is a lot of paperwork too.
There is other paperwork other than tax and immigration paperwork as well if you move your tax home, i.e. the FBAR form:
http://www.fincen.gov/forms/files/f9022-1_fbar.pdf - you may need to file this if you maintain a Canadian bank account/RRSP
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Steve.