We already know, of course, that our government moved mountains to help the banks during the crisis. But the report adds to our understanding of events by describing how the Treasury Department changed the tax code to benefit banks acquiring weaker institutions. Never mind that the Constitution allows only Congress to write tax rules. I.R.S. Notice 2008-83 came out of nowhere on Sept. 30, 2008, the report noted on Page 371. It removed existing limits on the use of tax losses that could be taken by a bank when it acquired a troubled institution. The change appeared just as Citigroup was mounting its $1-a-share bid for Wachovia. … Two days after the tax change, Wells Fargo topped Citi’s proposal by offering $7 a share. The change in the code had made such a deal more economical for Wells because it could reduce its taxable income by $3 billion in the first year after acquiring Wachovia. Previously, Wells could have reduced its income by just $1 billion in Year 1. “They were changing the rules on the fly to the apparent advantage of banks who wanted to get something for nothing out of this crisis,” said Janet Tavakoli, president of Tavakoli Structured Finance in Chicago. “Why aren’t people being questioned and held accountable for that?” As it turned out, Wells did not benefit from the code change because it had no taxable income to offset, the report said. I.R.S. Notice 2008-83 was repealed in 2009.