"Audits in 2010 of large corporations (>$250 million in assets) turned up $23.7 billion dollars in unreported taxes. This had dropped in half to just $12.5 billion during FY 2018," said the report. 

Finally, criminal convictions, which have been steadily dropping since the 1980s, reached an all-time low of 928 last year, and of these, 530 were for tax fraud rather than other types of offenses such as identity theft or money laundering. The report noted that convictions have dropped by 63 percent in just five years, and 75 percent over 25 years. 

"IRS of course has major responsibility for not only going after tax cheats who don't pay their taxes on legal sources of income, but also for tax evaders that fail to report and pay taxes on illegally gotten gains," said the report. 

The report noted that, due to continuous budget cuts, IRS personnel has dropped 22 percent since 2010. The number of revenue agents specifically has dropped 35 percent; the number of tax examiners has dropped 17 percent; and the number of criminal investigators has dropped 27 percent.