Section 6 CGST Act

(1) Without prejudice to the provisions of this Act, the officers appointed under the State Goods and Services Tax Act or the Union Territory Goods and Services Tax Act are authorised to be the proper officers for the purposes of this Act, subject to such conditions as the Government shall, on the recommendations of the Council, by notification, specify.
(2) Subject to the conditions specified in the notification issued under sub-section (1),––
(a) where any proper officer issues an order under this Act, he shall also issue an order under the State Goods and Services Tax Act or the Union Territory Goods and Services Tax Act, as authorised by the State Goods and Services Tax Act or the Union Territory Goods and Services Tax Act, as the case may be, under intimation to the jurisdictional officer of State tax or Union territory tax;
(b) where a proper officer under the State Goods and Services Tax Act or the Union Territory Goods and Services Tax Act has initiated any proceedings on a subject matter, no proceedings shall be initiated by the proper officer under this Act on the same subject matter.
(3) Any proceedings for rectification, appeal and revision, wherever applicable, of any order passed by an officer appointed under this Act shall not lie before an officer appointed under the State Goods and Services Tax Act or the Union Territory Goods and Services Tax
Act.