Woofy pulled this off the Canadian Banker’s Association website:
I am not a U.S. person. What does FATCA mean for me?
The majority of Canadians are not U.S. persons and, in most cases, FATCA will have little impact. If you have an existing account and there is an indication that you may be a U.S. person, or if you are opening a new account, your financial institution may ask you to provide additional information or documentation to demonstrate that you are not a U.S. person.
If you choose not to provide this additional documentation upon request, at a minimum, your financial institution may be required to withhold a tax of 30% on U.S. source payments that you receive and send this money to the IRS.
This is really just a game. The CBA should just tell the IRS to take their regulations and shove it. How can people prove that they are not US persons for tax purposes? Imagine the following scenarios: