35 ILCS 505/12
It is the duty of every distributor, receiver, and supplier under this Act to keep within this State or at some office outside this State for any period for which the Department is authorized to issue a Notice of Tax Liability to the distributor, receiver, or supplier records and books showing all purchases, receipts, losses through any cause, sales, distribution and use of motor fuel, aviation fuels, home heating oils, and kerosene, and products used for the purpose of blending to produce motor fuel, which records and books shall, at all times during business hours of the day, be subject to inspection by the Department, or its duly authorized agents and employees. For purposes of this Section, "records" means all data maintained by the taxpayer including data on paper, microfilm, microfiche or any type of machine-sensible data compilation. The Department may, in its discretion, prescribe reasonable and uniform methods for keeping of records and books by licensees and that set forth requirements for the form and format of records that must be maintained in order to comply with any recordkeeping requirement under this Act.
35 ILCS 505/12