For 'accidental Americans,' the hidden costs prove taxing

Tom Wallis was born in France to a French mother and American father. But his father passed away when he was just six years old. Apart from one year he spent working in the United States, Wallis has spent little time tending to his American roots – he thinks of himself as French.

But four years ago, his sister tried to apply for a loan. Her French bank asked her to declare whether she was American, and knowing her father's lineage, she replied yes. That's when she, and her siblings discovered they owed the American government tens of thousands of dollars in taxes – with Mr. Wallis alone on the hook for more than $100,000.

“We had to tell the French banks that we were