United States taxpayers have an obligation report their interest in any foreign financial accounts with regard to the balances in those accounts. If the aggregate balance of all such accounts exceeds $10,000 at any point during the year then you are also required to file a Foreign Bank Account Report (FBAR).
Despite this legal requirement, many taxpayers do not file required FBARs. Some may be unaware of the requirement, particularly if they are not a U.S. citizen, but are required to file a tax return because they are “green card” holders or have been substantially present in the United States. Other violations may be less excusable, or—as the IRS designates them— “willful”.
If you have undisclosed foreign financial accounts, you should consult with a tax attorney with FBAR experience, determine your exposure to risk, and select a course of action to minimize that risk.