The IRS along with the DOJ has been aggressively pursuing offshore account holders to disclose their overseas bank accounts before it's too late.  There are significant penalties for holding accounts in certain foreign banks.  However, in an effort to encourage account holders to disclose their accounts, the IRS started the Offshore Voluntary Disclosure Program (OVDP)  and the streamlined procedures enable taxpayer to meet their tax obligations while limiting the potential penalties for continued non-compliance.

Criminal Investigations can be initiated from information obtained from within the IRS when a revenue agent (auditor) or revenue officer (collection) detects possible fraud.  Information is also routinely received from the public as well as from ongoing investigations underway by other law enforcement agencies or by United States Attorneys offices across the country.