Senate Finance Committee Chairman Ron Wyden (D-Ore.), and Sen. Sheldon Whitehouse, (D-R.I.), launched an investigation April 28 into whether political interference affected a 2015 grand jury investigation of Caterpillar Inc. and its alleged practice of holding profits in a Swiss subsidiary, allegedly to avoid higher tax rates in the U.S.

They also seek to determine if former Attorney General William Barr was involved.

"Since January 2018, the IRS has sought to recover $2.3 billion in unpaid taxes and penalties from Caterpillar in connection with the alleged tax practices," Whitehouse and Wyden wrote to Attorney General Merrick Garland and Internal Revenue Service Commissioner Charles Rettig.

"Alarmingly, just six days after Barr was nominated to serve as Attorney General, an inspector general agent at the U.S. Federal Deposit Insurance Corp. was reportedly instructed by the DOJ tax division and the Office of the Deputy Attorney General ‘that no further action was to be taken on the [Caterpillar] matter until further notice,'" the letter continues.

"The investigation has reportedly been ‘stalled’ since this order was issued and many questions remain unanswered about the decision and what ethics guidance was provided to Mr. Barr regarding the matter.”

The letter asked for all documents and communications from the day Barr was hired in 2019 as attorney general—between any employee of the White House and any unofficial adviser to the president with any employees of the DOJ and IRS involved with the Caterpillar matter and the investigation of a separate company, Renaissance Holdings, related to tax matters.

Barr, previously at law firm Kirkland & Ellis, had been hired by Caterpillar to represent the firm in the tax investigation before being named attorney general, after several Caterpillar offices were searched by federal agents in 2017, presumably as part of the grand jury investigation.

Deerfield, Ill-based Caterpillar did not respond to requests for comment. But the company and its accountant, PriceWaterhouseCoopers LLP, previously defended the equipment provider's tax practices and told the Senate Finance Subcommittee in 2014 that it complied with the law.

Whitehouse, who is chairman of the Senate subcommittee on federal courts, also asked A.G. Garland in the letter if the DOJ tax division authorized any declinations to prosecute related to criminal tax matters arising out of grand jury investigations into Caterpillar, and if so, inquired whether the U.S. Attorney’s Office for the Central District of Illinois submitted a written request for reconsideration explaining why prosecution is warranted. 

The U.S. Attorney's Office could neither confirm nor deny any previous or current investigation into Caterpillar. The U.S. Attorney for the Northern District also declined to comment.