The mystery of last week's Caterpillar office raid by various US government agencies may have been resolved, after the NYT reported overnight that a report commissioned by the government, written by an accounting professor at the Tuck School of Business at Dartmouth, has accused the heavy-equipment maker of carrying out tax and accounting fraud.

"Caterpillar did not comply with either U.S. tax law or U.S. financial reporting rules," wrote Leslie A. Robinson, an accounting professor at the Tuck School of Business at Dartmouth College and the author of the report. "I believe that the company's noncompliance with these rules was deliberate and primarily with the intention of maintaining a higher share price. These actions were fraudulent rather than negligent."

CAT spokeswoman Corrie Heck Scott said that the company had not been provided with a copy of the report and declined to comment further. The company has defended its tax strategies in previous years by calling the arrangements prudent and lawful among large United States companies, despite repeatedly falling in hot water with the government over its tax practices which have been a focus of government investigators since a 2014 Senate hearing found that the company cut its tax bill by $2.4 billion over 13 years, moving earnings out of the United States and into a Swiss subsidiary, despite internal company warnings that the strategy lacked a business purpose, other than tax avoidance. Less than a year later, Caterpillar disclosed it received a subpoena from federal investigators seeking documents and information relating to the movement of cash among domestic and overseas subsidiaries, as well as other matters involving its foreign units, including the Swiss entity.

The company has since disclosed in securities filings that the Internal Revenue Service is seeking more than $2 billion in income taxes and penalties on profits earned by the Swiss unit. Caterpillar has said it is "vigorously contesting" the I.R.S.'s proposed increases.

Robinson's 85-page analysis is based on publicly available and internal financial data of the company, she wrote in the report, as well as bank data tracking wire transfers from Switzerland into the United States. In the report, Robinson estimated that Caterpillar has brought back $7.9 billion into the States, structured as loans, over and beyond the income that had already been taxed overseas. She concluded that the company failed to report those loans for tax or accounting purposes, and she wrote that those profits should be subject to federal taxes.

Robinson's report focused on one specific part of Caterpillar's offshore tax arrangement. It concluded that the company failed to pay taxes on billions of dollars brought home primarily from its Swiss unit and its affiliates, and thus failed to comply with United States tax law and financial reporting rules. Robinson wrote that she was asked to provide a written opinion of Caterpillar's financial reporting related to various tax accounting standards, "as pertaining to" the investigation of Caterpillar by the Federal Deposit Insurance Corporation Office of Inspector General.

"I was provided with all documents available to the case agents assigned to the investigation," Ms. Robinson wrote. She also wrote that she spent approximately 200 hours reviewing the evidence and performing calculations.

In one example, she cited correspondence between the company and the Securities and Exchange Commission in which Caterpillar said it had $2.5 billion of income eligible to be brought to the United States tax-free. Ms. Robinson wrote that her research showed that the company did not have "anywhere near" that sum still available to be brought in tax-free.

Caterpillar failed to report those loans as taxable distributions of cash, thus avoiding the tax on earnings brought home from Switzerland, while "enjoying the use of those earnings to meet U.S. cash needs," she wrote.

The report does not explain whether Caterpillar used the type of creative, and often legal, transactions that United States multinationals use to avoid tax on earnings brought home from offshore.

The NYT adds that while no charges have been filed, and it is not clear whether investigators agree with the findings or intend to act on them, last week's bust at three CAT offices, including its Peoria HQ may be validation that the government is indeed probing the allegations. The report, which has not been made public or made available to Caterpillar, outlines a company strategy for bringing home billions of dollars from offshore affiliates while avoiding federal income taxes on those earnings.

In 2012, the same Senate committee that examined Caterpillar's taxes found that Hewlett-Packard stitched together a series of such loans to bring home billions of dollars tax-free. The 2014 Senate report on Caterpillar said the company worked with the accounting firm PricewaterhouseCoopers, to set up its Swiss tax-cutting strategy. PwC was also the company's auditor, which raised "significant conflict of interest concerns," according to Senate investigators.

The report by Ms. Robinson makes a passing reference to PwC but does not address what role, if any, it had in these transactions.

CAT stock was down 3.5% premarket on the news, after plunging last week after news of the office raid broke.