215 ILCS 5/131.13
Every company which is authorized to do business in this State and which is a member of an insurance holding company system must register with the Director, except a foreign or alien company subject to registration requirements and standards adopted by statute or regulation in the jurisdiction of its domicile which are substantially similar to those contained in this section and Sections 131.14 through 131.20a . Any company which is subject to registration under this section must register within 60 days after the effective date of this Article or 15 days after it becomes subject to registration, whichever is later, unless the Director for good cause shown extends the time for registration, and then within such extended time. The Director may require any authorized company which is a member of a holding company system which is not subject to registration under this section to furnish a copy of the registration statement or other information filed by such company with the insurance regulatory authority of its domiciliary jurisdiction.
215 ILCS 5/131.13