The original tax IRS whistleblower law covered tax frauds and underpayment of taxes. However, there was widespread disagreement as to the scope of the law, and whether or not the law covered criminal tax frauds and/or sanctions paid for IRS-related infractions.
The law firm of Kohn, Kohn and Colapinto, working with the National Whistleblower Center and tax attorney Dean Zerbe led the fight to clarify the tax whistleblower law. In 2017, they won a landmark ruling in Tax Court broadening the scope of the tax whistleblower law. The Department of Treasury appealed this ruling. While the case was under appeal Congress amended the law to include any law or regulation for which a form is filed with the IRS, or is within the jurisdiction of the IRS criminal division.
In 2018 Congress amended the tax whistleblower law to broaden the scope of coverage explicitly. In response to that law, the Department of Treasury dropped their appeal of the Tax Court case.