35 ILCS 5/914
For the purpose of administering and enforcing the provisions of this Act, the Department, or any officer or employee of the Department designated, in writing, by the Director may hold investigations and hearings concerning any matters covered by this Act that are not otherwise delegated to the Illinois Independent Tax Tribunal, and may examine any books, papers, records or memoranda bearing upon such matters, and may require the attendance of any person, or any officer or employee of such person, having knowledge of such matters, and may take testimony and require proof for its information. In the conduct of any investigation or hearing, neither the Department nor any officer or employee thereof shall be bound by the technical rules of evidence, and no informality in any proceeding, or in the manner of taking testimony, shall invalidate any order, decision, rule or regulation made or approved or confirmed by the Department. The Director, or any officer or employee of the Department authorized by the Director shall have power to administer oaths to such persons. 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 or by a computer print-out of Department records, under the certificate of the Director. If reproduced copies of the Department's books, papers, records or memoranda are offered as proof, the Director must certify that those copies are true and exact copies of such records on file with the Department. If computer print-outs of records of the Department are offered as proof, the Director must certify that those computer print-outs are true and exact representations of records properly entered into standard electronic computing equipment, in the regular course of the Department's business, at or reasonably near the time of the occurrence of the facts recorded, from trustworthy and reliable information. Such reproduced copy shall, without further proof, be admitted into evidence before the Department or in any legal proceeding.
35 ILCS 5/914