Today IRS issued IRS Newswire Number IR-2015-135, ttitled: "IRS Criminal Investigation Releases Fiscal Year 2015 Annual Report".
In particular pages 18 and 19 give examples of "Non-filer Investigations".
Page 18 of this report states: "Taxpayers who fail to file income tax returns and effectively stop paying income tax, pose a serious threat to tax administration and the American economy. Criminal investigation devotes investigative resources to individuals who simply refuse to comply iwht the law."
Pages 18 and 19 of this report cites specific names of an attorney, a businessman, and a chef, who received prison sentences and fines for failing to file federal income tax returns!