Ill. Admin. Code. tit 86, § 1050.400 - Electronic Notice and Filing Requirements; Books and Records

a) Unless otherwise provided, all applications, notices, filings, certificates, or other documents required by this Part to be submitted to or issued by the Department shall be made by electronic means.

b) Permanent endowment funds and taxpayers shall maintain books and records under this Part and make them available upon request by the Department.

c) Permanent endowment funds shall maintain their books and records for no less than three years. Taxpayers shall maintain their books and records in accordance with the Illinois Income Tax Act and regulations promulgated thereunder.