205 ILCS 740/4
No collection agency shall operate in this State, directly or indirectly engage in the business of collecting debt, solicit debt claims for others, have a sales office, a client, or solicit a client in this State, exercise the right to collect, or receive payment for another of any debt , without obtaining a license under this Act except that no collection agency shall be required to be licensed if the agency's activities in this State are limited to collecting debts from debtors located in this State by means of interstate communication, including telephone, mail, or facsimile transmission, electronic mail, or any other Internet communication from the agency's location in another state provided they are licensed in that state and these same privileges are permitted in that licensed state to agencies licensed in Illinois.
205 ILCS 740/4