From The New Yorker:
Let’s be clear: Romney did nothing wrong. As he said in last night’s debate, he and his wife paid the U.S. government what they owed, and not a penny more. Like many very wealthy people, they appear to have employed a small army of financial advisers and a perfectly reputable accounting firm, PricewaterhouseCoopers, to minimize their tax exposure using a range of methods. Over the years, these methods have included setting up tax-sheltered retirement vehicles, establishing family trusts, making offshore investments, and exploiting one particular tax break that Romney was entitled to use by dint of his employment at Bain Capital. By now, you’ve probably seen the headlines about the returns. In 2010 and 2011, Romney and his wife made $42.6 million, almost all of it in the form of income from their various investments, which is taxed at a rate of fifteen per cent. In those two years, the Romneys paid the federal government $6.2 million. Confirming what Mitt said in New Hampshire last week, their effective tax rate in 2011 will be 15.4 per cent. In 2010, they did a bit better, at 13.9 per cent.
More here.