With all due respect, tiger is the only one who knows what he's talking about. There is a Treaty between Canada and the US that provides that each others dividend income received by non-taxable IRAs is NOT taxable and there should be no withholding.It has been my experience that Canada does withhold for some brokers and not others. Your brokerage has to inform Canada that this is a non-taxable account. If they do withhold there is a Canadian tax form who's number I've long forgotten that you can file to get the withholding back from Canada. Problem is, you have to file for eaach dividend payment. Better to change brokerages. YOU ABSOLUTELY CANNOT GET A TAX CREDIT FOR WITHHELD CANADIAN TAXES ON YOUR US TAX RETURN.

Think about it. If the dividend goes to a non-taxable account it will not be taxed when withdrawn from the account as it will be in a regular account. The US will not give you a tax credit for foreign tax withholding associated with a non-taxable account when the US will never tax that income.