(a) If it is determined that a deficiency is due in respect of income, estate, or gift tax and the taxpayer has filed a petition with the Tax Court before (1) the adjudication of bankruptcy 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 a receiver, the trustee, receiver, debtor in possession, or other like fiduciary, may, upon his own motion, be made a party to the Tax Court proceeding and thereafter may prosecute the appeal before the Tax Court as to that particular determination. No petition shall be filed with the Tax Court for a redetermination of the deficiency after the adjudication of bankruptcy, the filing or (where approval is required by the Bankruptcy Act) the approval of a petition of, or the approval of a petition against, any taxpayer in any other bankruptcy proceeding, or the appointment of the receiver.

(b) Even though the determination of a deficiency is pending before the Tax Court for redetermination, proof of claim for the amount of such deficiency may be filed with the court in which the proceeding under the Bankruptcy Act or receivership proceeding is pending without awaiting final decision of the Tax Court. In case of a final decision of the Tax Court before the payment or the disallowance of the claim in the proceeding under the Bankruptcy Act or receivership proceeding, a copy of the Tax Court's decision may be filed by the district director with the court in which such proceeding is pending.

(c) While a district director is required by section 6871(a) and paragraph (a) of §301.6871(a)-1 to make immediate assessment of any deficiency, such assessment is not made as a jeopardy assessment within the meaning of section 6861, and consequently the provisions of that section do not apply to any assessment made under section 6871. Therefore, the notice of deficiency provided in section 6861(b) will not be mailed. Although such notice will not be issued, a letter will be sent to the taxpayer or to the trustee, receiver, debtor in possession, or other like fiduciary, notifying him in detail how the deficiency was computed, that he may furnish evidence showing wherein the deficiency is incorrect, and that upon request he will be granted a conference by the district director with respect to such deficiency. However, such letter will not provide for such a conference where a petition was filed with the Tax Court before (1) the adjudication of bankruptcy in a liquidating proceeding, (2) the filing with a court of competent jurisdiction or (where approval is required by the Bankruptcy Act), 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 a receiver.