IRS ‘Black Hole’ Swallows Whistleblower Against Koch, Walmart (1)

Charles Middleton has spent almost 10 years wondering whether becoming a whistleblower to the IRS was worth it.

A former senior tax executive at Walmart Inc. and billionaire Bill Koch’s Oxbow Carbon LLC, Middleton in 2009 filed the first of several confidential claims he’s made against his employers. He asserted, in hundreds of pages of documents obtained by Bloomberg Tax, that those companies engaged in questionable practices that he estimated resulted in more than $250 million in tax dodges by Walmart and $350 million by Koch’s business—allegations both companies vehemently deny.