I just offer to help them file a Form 211

The IRS Whistleblower Office pays money to people who blow the whistle on persons who fail to pay the tax that they owe. If the IRS uses information provided by the whistleblower, it can award the whistleblower up to 30 percent of the additional tax, penalty and other amounts it collects.

https://www.irs.gov/compliance/whistleblower-informant-award