JM 6-6.100
The Attorney General has plenary power to compromise or settle any civil or criminal case that arises under the internal revenue laws and that the IRS refers to the Department of Justice for prosecution or defense. See 38 U.S. Op. Atty. Gen. 98 (1934). No compromise or settlement is final until approved in writing by the Attorney General or an authorized delegate.
[updated April 2018]