Walmart, the world’s biggest retail company, underpaid US taxes on nearly $2 billion worth of offshore cash, according to whistleblower documents filed by a former Walmart executive to the Internal Revenue Service (IRS) in 2011, and recently obtained by Quartz. From the report: The firm avoided nearly $200 million in taxes on that money and “dramatically” overstated its foreign tax credits in 2009 and 2010 by routing payments from Luxembourg to the United States via the United Kingdom and not declaring they came from a tax haven, the whistleblower wrote. If Walmart claimed all the tax credits, it could have improperly avoided paying close to $600 million in total via the maneuvers, according to the files. The whistleblower argued in the documents that the company should owe all that money to the IRS. A second former executive, who shared the files with Quartz, confirmed the whistleblower’s allegations. Walmart denied any wrongdoing. “The transactions brought to our attention were appropriately reported to and audited by the IRS,” a spokesman said in an emailed statement. “The tax years covering this matter were closed by the IRS more than seven years ago.” The spokesman declined to say whether the company explicitly told the IRS that the money originated in Luxembourg, rather than the United Kingdom.