Posted: Mon Jul 14, 2008 10:38 am-
In this case tax treaty benefits exempt you from US withholding. The SSA is supposed to withhold 30% on 85% of the income from social security but if you claim a tax treaty benefit (Form 8840 or 8833) there is no withholding (so claim it, obviously).
But you still get taxed on it at the marginal rate of income tax, and you still have to file a 1040NR and an 8840 or 8833, depending on the circumstances.
You can't remain an LPR I'm afraid if you move to Canada, because if you did you would face dual taxation. Under the tax treaty a claim of permanent residence makes you subject to tax in that jurisdiction, so if you are an LPR in the US and you live in Canada, you are subject to tax in both places and there's no way around it.
If you want to retain the right to reside in the US at some future point, you should apply for US citizenship.
This subjects you to a different tax situation because US citizens must file a 1040 every year even if they are non-resident. You would be taxed on your US source income (e.g. social security, but excluding bank interest, if you file Form W-8BEN) and claim a foreign tax credit in the US (Form 2555) for any tax paid in Canada on other worldwide income.
The only major downside to doing this is that the foreign tax credit in the US maxes out at $85,700 (last year) so any income you received above that would be subject to dual taxation.
So basically, if you reckon your income in retirement every year will be under that limit, apply for US citizenship. If you reckon it will be over that amount, you'd have to give up your LPR status.
Note that long-term residents of the US (8 years or more in the last 15 years) have to file tax paperwork for ten years anyway after they give up their status in the US and can still be taxed on US-source income, so in your situation I'd say there are only going to be trivial benefits to not applying for US citizenship. Basically it saves you some paperwork if you live into your mid-70s, unless of course you're still earning heaps then.
Read the instructions for Form 1040NR.
As for how you receive the payments from the SSA, I think you have to use a US bank account. Better to do it that way anyway because of the fluctuations in exchange rates.
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Steve.