The Citadel founder requested the information last month as part of his lawsuit against the Internal Revenue Service, according to a filing Tuesday in federal court in Miami. Griffin claims in the suit that the IRS failed to establish “appropriate administrative, technical, and/or physical safeguards” to protect his private data.

ProPublica published tax information last year about many of the wealthiest US taxpayers, including Griffin. It reported he had an average annual income of almost $1.7 billion between 2013 and 2018 and paid an average federal tax rate of 29.2% during that time. Billionaires including Jeff Bezos and Elon Musk had in some years paid minimal or no income tax even as their fortunes soared, ProPublica reported.

A ProPublica spokesperson said it received “sprawling” subpoenas from Griffin’s lawyers, and it doesn’t know the identity of the source who provided the tax information.

“We are deeply committed to protecting our sources — who are the lifeblood of our journalism — and the independence of our newsroom,” the spokesperson said. “This is sacrosanct at ProPublica and will remain our priority as we address Griffin’s subpoenas.”

In April, the IRS urged a judge to dismiss the lawsuit, saying Griffin speculates that unknown people in an organization of nearly 80,000 employees exploited security weaknesses to obtain his return information while “omitting or discounting all other possibilities or explanations.”

Settlement ‘Unlikely’

The case has been referred to a mediator, Elaine E. Feldman, and a settlement is “unlikely at this time,” according to the Tuesday filing, which is a status report from lawyers for Griffin and the IRS.

Griffin will press the fight because a leak of thousands of taxpayers’ records is “an affront to all citizens,” Citadel spokesperson Zia Ahmed said in a statement.

“The IRS has a fundamental obligation to protect the confidentiality of Americans’ sensitive financial information,” Ahmed said. “Ken is fighting to ensure that the IRS upholds its obligations and the individuals and entities behind this leak are held responsible.”

Griffin has a net worth of $37 billion, according to the Bloomberg Billionaires Index.

Michael Bloomberg, majority owner of Bloomberg News parent Bloomberg LP, was among those included in the reporting.

Beyond its series, “The Secret IRS Files,” ProPublica has reported extensively this year on US Supreme Court Justice Clarence Thomas and his financial ties to Republican megadonor Harlan Crow, including luxury vacations, private jet flights, real estate transactions, and school tuition payments for a family member. The reports have heightened scrutiny of the justices and come amid a lack of transparency and an ethics code at the court.

The case is Griffin v. Internal Revenue Service, 22-cv-24023, US District Court, Southern District of Florida (Miami).