Filing returns; keeping returns confidential; destroying returns

(a) All monthly and annual returns shall be transmitted in the form and manner prescribed by the department. (b) All tax returns and return information required to be filed under this chapter, and the report of any investigation of the return or of the subject matter of the return, shall be confidential. It shall be unlawful for any person or any officer or employee of the State, including the auditor or the auditor's agent with regard to tax return information obtained pursuant to section 23-5(a), to intentionally make known information imparted by any tax return or return information filed pursuant to this chapter, or any report of any investigation of the return or of the subject matter of the return, or to wilfully permit any return, return information, or report so made, or any copy thereof, to be seen or examined by any person; provided that for tax purposes only, the taxpayer, the taxpayer's authorized agent, or persons with a material interest in the return, return information, or report may examine them. Unless otherwise provided by law, persons with a material interest in the return, return information, or report shall include: (1) Trustees; (2) Partners; (3) Persons named in a board resolution or a one per cent shareholder in the case of a corporate return; (4) The person authorized to act for a corporation in dissolution; (5) The shareholder of an S corporation; (6) The personal representative, trustee, heir, or beneficiary of an estate or trust in the case of the estate's or decedent's return; (7) The committee, trustee, or guardian of any person in paragraphs (1) through (6) who is incompetent; (8) The trustee in bankruptcy or receiver, and the attorney-in-fact of any person in paragraphs (1) through (7); (9) Persons duly authorized by the State in connection with their official duties; (10) Any duly accredited tax official of the United States or of any state or territory; (11) The Multistate Tax Commission or its authorized representative; (12) Members of a limited liability company; and (13) A person contractually obligated to pay the taxes assessed against another when the latter person is under audit by the department. Any violation of this subsection shall be a class C felony. (c) The department may destroy the monthly returns filed pursuant to section 237-30, or any of them, upon the expiration of three years after the end of the calendar year in which the taxes so returned accrued.