For the purpose of administering and enforcing the provisions of this chapter, the department or any officer, agent, or employee of the department designated by the executive director in writing or by regulation may:
(1) Hold investigations concerning any matters;
(2) Require the attendance of any individual, or any officer or employee of a taxpayer, having knowledge of such matters; and
(3) Take testimony and require proof for its information.
In the conduct of any investigation, neither the department nor any officer, agent, or employee thereof shall be bound by the technical rules of evidence, and the informality in any proceeding or in the manner of taking testimony shall not invalidate any order, decision, rule, or regulation made or approved or confirmed by the department. Any officer or employee of the department authorized by the executive director or regulation shall have power to administer oaths. The books, papers, records, and memoranda of the department, or parts thereof, may be proved in any investigation or legal proceeding by a reproduced copy thereof, under the certificate of the executive director, and any such reproduced copy shall, without further proof, be admitted into evidence before the department or in any legal proceeding.