35 ILCS 130/10
The Department, or any officer or employee designated in writing by the Director thereof, for the purpose of administering and enforcing the provisions of this Act, may hold investigations and, except as otherwise provided in the Illinois Independent Tax Tribunal Act of 2012, may hold hearings concerning any matters covered by this Act, and may examine books, papers, records or memoranda bearing upon the sale or other disposition of cigarettes by a distributor, secondary distributor, retailer, manufacturer with authority to maintain manufacturer representatives under Section 4f of this Act, or manufacturer representative, and may issue subpoenas requiring the attendance of a distributor, secondary distributor, retailer, manufacturer with authority to maintain manufacturer representatives under Section 4f of this Act, or manufacturer representative, or any officer or employee of a distributor, secondary distributor, retailer, manufacturer with authority to maintain manufacturer representatives under Section 4f of this Act, or any person having knowledge of the facts, and may take testimony and require proof, and may issue subpoenas duces tecum to compel the production of relevant books, papers, records and memoranda, for the information of the Department.
All hearings to contest administrative decisions of the Department conducted as a result of a protest filed with the Illinois Independent Tax Tribunal on or after July 1, 2013 shall be subject to the provisions of the Illinois Independent Tax Tribunal Act of 2012.
In the conduct of any investigation or hearing provided for by this Act, neither the Department, nor any officer or employee thereof, shall be bound by the technical rules of evidence, and no informality in the proceedings nor in the manner of taking testimony shall invalidate any rule, order, decision or regulation made, approved or confirmed by the Department.
The Director of Revenue, or any duly authorized officer or employee of the Department, shall have the power to administer oaths to such persons required by this Act to give testimony before the said Department.
The books, papers, records and memoranda of the Department, or parts thereof, may be proved in any hearing, investigation or legal proceeding by a reproduced copy thereof under the certificate of the Director of Revenue. Such reproduced copy shall, without further proof, be admitted into evidence before the Department or in any legal proceeding.
35 ILCS 130/10