(a) Upon (1) the adjudication of bankruptcy of any taxpayer in any liquidating proceeding, (2) the filing with a court of competent jurisdiction or (where approval is required by the Bankruptcy Act, 11 U.S.C. Chapters 1-14) the approval of a petition of, or the approval of a petition against, any taxpayer in any other proceeding under the Bankruptcy Act, or (3) the appointment of any receiver for any taxpayer in a receivership proceeding before any court of the United States or of any State or Territory or of the District of Columbia, the district director shall immediately assess any deficiency of income, estate, or gift tax (together with all interest, additional amounts, or additions to the tax provided by law), determined by him, if such deficiency has not heretofore been assessed in accordance with law. Such assessment shall be made immediately, whether or not a notice of deficiency has been issued, and without regard to the restrictions upon assessment under section 6213.

(b) As used in this section and §§ 301.6871(a)-2 to 301.6873-1, inclusive, the term “proceeding under the Bankruptcy Act” includes a proceeding under chapters I to VII, inclusive, of the Bankruptcy Act, or under section 75 or 77 (11 U.S.C. 203,205,or,inclusive,of,or.