35 ILCS 195/3-25: Sourcing.

As used in this Act, the term "in this State" means at a physical location within this State for a sale occurring in person. For a sale occurring electronically or by phone, there shall be a rebuttable presumption that the customer requesting the sale is located in this State if the customer's contact information associated with a device or account on record with or available to a digital asset broker indicates an Illinois home address, an Illinois mailing address, or an Illinois internet protocol address or other data showing "place of primary use" in Illinois, as defined in the Mobile Telecommunications Sourcing Conformity Act. The burden of proving that a customer is not located in this State is on the digital asset broker. For administrative ease, a digital asset broker may create reasonable categorization standards to use in analyzing data to determine if a customer is located in Illinois; however, its reliance on such standards does not alleviate the digital asset broker's burden of proof.