(1) In discharging their functions by or under this Act, the Tribunal and the Commissioner shall have all the powers of a Civil Court for the purpose of,-
(a) proof of facts by affidavit ;
(b) summoning and enforcing the attendance of any person, and examining him on oath or affirmation ;
(c) compelling the production of documents ; and
(d) issuing commissions for the examination of witnesses.
(2) In the case of any affidavit to be made for the purposes of this Act, any officer appointed by the Tribunal or the Commissioner may administer the oath to the deponent.
(3) Without prejudice to the provisions of any other law for the time being in force, where a person, to whom a summons is issued by the Tribunal or the Commissioner either to attend to give evidence or produce books of accounts, registers or other documents at a certain place and time, intentionally omits to attend or produce the books of accounts, registers or documents at the place and time, the Tribunal or, as the case may be, the Commissioner, may impose on him such fine not exceeding five thousand rupees as it or he thinks fit; and the fine so levied may be recovered in the manner provided in this Act for recovery of arrears of tax :
Provided that, before imposing any such fine, the person concerned shall be given a reasonable opportunity of being heard.
(4) When any documents are produced by a person or dealer on whom the summons was issued by the Commissioner and the Commissioner is of the opinion that such dealer or any other dealer has evaded or is attempting to evade the payment of any tax due from him and the documents produced by such dealer or person are necessary for establishing the case against such dealer, the Commissioner may, for reasons to be recorded in writing, impound the documents and shall grant a receipt for the same and retain the same for so long as may be necessary in connection with the proceedings under this Act [or for a prosecution] :
Provided that, if the original documents are required by any statutory authority for any official purpose, then the said documents shall be made available to such authority for such purpose for such duration as may be required.