625 ILCS 5/3-402.2
In addition to audit authority set forth in Section 2-124 of this Act, the Secretary of State, when this state is the base jurisdiction, may audit such owners displaying a base plate of this state as to authenticity of mileage figures and registrations and at such time and frequency as determined by the Secretary of State. Audits may be made by officials of other jurisdictions which are members of an International Registration Plan (IRP) of which this state is also a member.
Upon completion of any such audit, the Secretary of State shall notify all jurisdictions in which such owner was proportionally registered on the accuracy of the records of such owner. Should such owner have underpaid or overpaid any jurisdiction in which his vehicles were proportionally registered, such information shall be furnished to the jurisdiction for processing in accordance with the procedures as set forth under the International Registration Plan.
625 ILCS 5/3-402.2