Ill. Admin. Code tit. 86 § 471.105
Beginning October 1, 2003, a tax is imposed upon the privilege of using in this State gas obtained in a purchase of out-of-State gas at the rate or rates set forth in Section 471.110 of this Part. [35 ILCS 173/5-10 ]
EXAMPLE: A purchase of out-of-State gas occurs when a purchaser enters into a contract outside of this State with a supplier to purchase gas at a wellhead located in Oklahoma. The purchaser then contracts with an Illinois utility for the delivery of that gas to the purchaser's place of business in Illinois. The sale of that gas occurs outside of this State and the seller is not liable for Gas Revenue Tax on the sale of that gas. Unless otherwise exempt under this Part, the purchaser incurs Gas Use Tax liability at the rate or rates set forth in Section 471.110 of this Part on the purchase of the out-of-State gas.
Ill. Admin. Code tit. 86, § 471.105