It is potentially very expensive to have a mistake in meeting the reporting requirements for foreign financial accounts. Without looking it up, my recollection is that the penalty for not (properly) reporting is 50% of the highest account balance in each account during the year messed up. That's too steep for me to even want to think about.

A number of years ago, I made the decision not to get involved in the preparation of any returns requiring that reporting, and to help refer any clients with the issue to preparer's who were experienced in that practice area. I sleep well giving up the few clients who have had that issue and getting to someone who knows better than I how to help them.

That is pretty much all I know on the subject.