26 U.S.C. § 6871

(a) Immediate assessment in receivership proceedings On the appointment of a receiver for the taxpayer in any receivership proceeding before any court of the United States or of any State or of the District of Columbia, any deficiency (together with all interest, additional amounts, and additions to the tax provided by law) determined by the Secretary in respect of a tax imposed by subtitle A or B or by chapter 41, 42, 43, or 44 on such taxpayer may, despite the restrictions imposed by section 6213(a) on assessments, be immediately assessed if such deficiency has not theretofore been assessed in accordance with law. (b) Immediate assessment with respect to certain title 11 cases Any deficiency (together with all interest, additional amounts, and additions to the tax provided by law) determined by the Secretary in respect of a tax imposed by subtitle A or B or by chapter 41, 42, 43, or 44 on— (1) the debtor’s estate in a case under title 11 of the United States Code, or (2) the debtor, but only if liability for such tax has become res judicata pursuant to a determination in a case under title 11 of the United States Code, may, despite the restrictions imposed by section 6213(a) on assessments, be immediately assessed if such deficiency has not theretofore been assessed in accordance with law. (c) Claim filed despite pendency of tax court proceedings In the case of a tax imposed by subtitle A or B or by chapter 41, 42, 43, or 44— (1) claims for the deficiency and for interest, additional amounts, and additions to the tax may be presented, for adjudication in accordance with law, to the court before which the receivership proceeding (or the case under title 11 of the United States Code) is pending, despite the pendency of proceedings for the redetermination of the deficiency pursuant to a petition to the Tax Court; but (2) in the case of a receivership proceeding, no petition for any such redetermination shall be filed with the Tax Court after the appointment of the receiver.