Right.
First of all, whether or not somebody is subject to U.S. tax, as a U.S. taxpayer, as a U.S. resident, or as a U.S. citizen, is a question of fact or law, or mixed fact and law. That stands separate from the intergovernmental agreement itself. The intergovernmental agreement is strictly about information reporting.
If the question is about how one sorts out an assertion by the U.S. that they're American residents for tax purposes, and they disagree with that, the tax treaty can have relevance to that in terms of determining the breaking of the tie between our two countries' laws. It was fine to be resident under both. Our tax treaty also sorts out for Canadian residents, and I mean real residents, who are U.S. citizens, and I mean real citizens, in terms of the pecking order of taxation.
But if you're speaking about the intergovernmental agreement itself, that's really a question between the taxpayer and the financial institution they're dealing with. Perhaps your question relates to what the financial institution does when the person says, “I am not a U.S. citizen.” In that circumstance, it's generally the case that the financial institution relies on what they're told by the person, in the absence of clear, contradictory evidence.
I'm sorry, I've tried to cover everything there.