US Canada dual tax year may have done US tax wrong

[lovetrees]

Oh dear. I thought I had it figured out. I know I am now late, but I am hoping that someone might still answer me. I did my US taxes but haven't sent them because while doing my Canadian forms I read information new to me, and now I think I might have done the US form wrong.

Is someone patient enough to advise me what to do?

I moved back to Canada mid Jan 09 after being in US on a TN all of 2008 and the last part of 07. I made less than 10k in the US in the first part of 09 so assumed I would do a dual status tax form, with end date in US the date I left. However, I read about substantial presence test, and when I calculate the number of days I was in the US I meet it, when I add vacation days in 09 to living there during 08, and some of 07.

So, my question is, do I have a choice of doing 1040NR Dual status, or must I do 1040 for full year, stating Canadian income and taxes paid?
Is there any point in sending in a request for extension while I figure this out or take it to an accountant, given that I am already late for US?
I did contribute to Canadian RRSP last year, is this of any consequence?
I read a bit about tax treaty. Does this apply to me?
If I do 1040 for full year to US, then what do I do for Canadian form?
Thankyou to anyone if you have the patience to answer. I did not expect to be in this spot.

[nelsona]

When you leave US to retunr to canada, regardless of SPT, you can declare yourself non-resident the moment you become Cdn tax resident. You would mention this on the 1040NR, where SPT is calculated.

If you do not owe US tax, then extension request is pointless.