The IRS has the authority to impose civil and criminal penalties for the failure to file Foreign Bank Account Reports (FBARs), but it is has the authority to impose lesser penalties, or none at all, in certain cases. If there is a reasonable cause for your FBAR violations, and your conduct was non-willful, you may not have to pay any penalties at all.
Internal Revenue Manual (IRM) 220.127.116.11 states that when an FBAR violation is found, the IRS examiner must either issue a Letter 3800 or issue a penalty. The Letter 3800 is warning letter notifying you of your apparent FBAR violations. Some taxpayers may get lucky and receive a warning without any FBAR penalties.
The civil penalties for non-willful FBAR violations are up to $10,000 per account per year, for up to six years. However, these are the maximum penalties allowable. The IRS has the discretion to reduce or eliminate the penalties in some cases.