Posted: Thu Aug 07, 2008 10:41 am-
1) Not unless you have Canadian-source income from employment or certain other sources, in this case you file a non-resident T1;
2) Have a look at the CRA website for the form;
3) Doesn't matter, it depends where they are resident now - if you're resident in Canada you file Canadian taxes, if you're resident in the US you file US taxes.
Bear in mind what "residency" means though as that is a complex area of tax law. However in your case you are a permanent resident, so under the tax treaty you HAVE to file a regular 1040 tax return every year. If you are self-employed you need to register as such and do payroll withholding, get a sales tax certificate (if you live in a State with sales tax), etc.
If you have residential ties to Canada (healthcare card, Canadian driver's licence, etc.) you must get rid of them. Canadian citizenship is not a residential tie.
This document gives you the information about residential ties:
http://www.cra-arc.gc.ca/E/pub/tg/p151/README.html
If you have an RRSP in Canada you must file Form 8891 every year to declare it to the IRS, you can no longer contribute to it, you would have to use an IRA.
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Steve.