Esther Thompson, 70, and her sister Betty, 69, both married to retired farmers living near Prince Albert, Sask., are among those who have come unhappily forward to the U.S. Internal Revenue Service under a voluntary disclosure program.

Unlike Canada, the United States requires its citizens, not just residents, to file tax returns and report their worldwide income.

Both Thompson sisters share joint accounts with their husbands and worry that penalties will be assessed on the days in which the accounts held significant sums after a big grain sale, for example, despite the fact that they were quickly drained to pay bills.

What’s more, the U.S. Foreign Account Tax Compliance Act (FATCA) will require Canadian financial institutions to disclose information about U.S. citizens who hold Canadian financial accounts or risk withholding taxes of 30% on all payments out of the United States. The FATCA requirements will kick in in 2014 and mean that many more Canadians will be identified to the U.S. authorities and could face harsh penalties on money they may no longer even have.

Yet, there are many Canadians with connections to the United States. Some estimates say there are 1 million living in the country. More than 316,000 people listed American as their “ethnic origin” in the 2006 census.