What happens if taxpayer who is required to file an FBAR and fails to do so?
Per the IRS, "failure to file an FBAR when required to do so may potentially result in civil penalties, criminal penalties or both. If you learn you were required to file FBARs for earlier years, you should file the delinquent FBAR reports and attach a statement explaining why the reports are filed late.
No penalty will be asserted if the IRS determines that the late filings were due to reasonable cause. Taxpayers are requested to keep copies of all relevant records."