815 ILCS 5/2.6
"Underwriter" means any person who has purchased a security from an issuer or a controlling person with a view to, or who offers or sells a security for an issuer or a controlling person in connection with, the distribution thereof, or who participates or has a participation in the direct or indirect underwriting of such distribution; but such term shall not include a person whose interest is limited to a commission or discount from an underwriter or dealer not in excess of the usual and customary distributors' or sellers' commission or discount. An underwriter shall be deemed to be no longer an underwriter of a security after he or she has completely disposed of his or her allotment of such security or, if he or she did not purchase the security, after he or she has ceased to offer and sell such security for the issuer or controlling person.
815 ILCS 5/2.6