430 ILCS 65/3(a) - "Except as provided in Section 3a, no person may knowingly transfer, or cause to be transferred, any firearm, firearm ammunition, stun gun, or taser to any person within this State unless the transferee with whom he deals displays either: (1) a currently valid Firearm Owner's Identification Card which has previously been issued in his or her name by the Department of State Police under the provisions of this Act; or (2) a currently valid license to carry a concealed firearm which has previously been issued in his or her name by the Department of State Police under the Firearm Concealed Carry Act. In addition, all firearm, stun gun, and taser transfers by federally licensed firearm dealers are subject to Section 3.1."

430 ILCS 65/3(a-10) - "Notwithstanding item (2) of subsection (a) of this Section, any person who is not a federally licensed firearm dealer and who desires to transfer or sell a firearm or firearms to any person who is not a federally licensed firearm dealer shall, before selling or transferring the firearms, contact a federal firearm license dealer under paragraph (1) of subsection (a-15) of this Section to conduct the transfer or the Illinois State Police with the transferee's or purchaser's Firearm Owner's Identification Card number to determine the validity of the transferee's or purchaser's Firearm Owner's Identification Card under State and federal law including the National Instant Criminal Background Check System. This subsection shall not be effective until January 1, 2024. Until that date the transferor shall contact the Illinois State Police with the transferee's or purchaser's Firearm Owner's Identification Card number to determine the validity of the card. The Department of State Police may adopt rules concerning the implementation of this subsection. The Department of State Police shall provide the seller or transferor an approval number if the purchaser's Firearm Owner's Identification Card is valid. Approvals issued by the Department for the purchase of a firearm pursuant to this subsection are valid for 30 days from the date of issue."

ISP Transfers page: https://verify.ispfsb.com/Public/Verify.aspx