"Affiliate" means a person that, with respect to another person: (i) has a direct or indirect ownership interest of more than 5% in the other person; or (ii) is related to the other person because a third person, or group of third persons who are affiliated with each other as defined in this subsection, holds a direct or indirect ownership interest of more than 5% in the related person.
"Marketplace" means a physical or electronic place, forum, platform, application or other method by which a marketplace serviceman makes or offers to make sales of service.
"Marketplace facilitator" means a person who, pursuant to an agreement with a marketplace serviceman, facilitates sales of service by that marketplace serviceman. A person facilitates a sale of service by, directly or indirectly through one or more affiliates, doing both of the following: (i) listing or otherwise making available a sale of service of the marketplace serviceman through a marketplace owned or operated by the marketplace facilitator; and (ii) processing sales of service for, or payments for sales of service by, marketplace servicemen.
"Marketplace serviceman" means a person that makes or offers to make a sale of service through a marketplace.
A marketplace facilitator shall determine on a quarterly basis, ending on the last day of March, June, September, and December, whether he or she meets the criteria of either paragraph (1) or (2) of this subsection (b) for the preceding 12-month period. If the marketplace facilitator meets the criteria of either paragraph (1) or (2) for a 12-month period, he or she is considered a serviceman maintaining a place of business in this State and is required to collect and remit the tax imposed under this Act and file returns for one year. At the end of that one-year period, the marketplace facilitator shall determine whether the marketplace facilitator met the criteria of either paragraph (1) or (2) during the preceding 12-month period. If the marketplace facilitator met the criteria in either paragraph (1) or (2) for the preceding 12-month period, he or she is considered a serviceman maintaining a place of business in this State and is required to collect and remit the tax imposed under this Act and file returns for the subsequent year. If, at the end of a one-year period, a marketplace facilitator that was required to collect and remit the tax imposed under this Act determines that he or she did not meet the criteria in either paragraph (1) or (2) during the preceding 12-month period, the marketplace facilitator shall subsequently determine on a quarterly basis, ending on the last day of March, June, September, and December, whether he or she meets the criteria of either paragraph (1) or (2) for the preceding 12-month period.
35 ILCS 110/2d