305 ILCS 5/10-4
The administrative enforcement unit within the authorized area of its operation shall notify each responsible relative of an applicant or recipient, or responsible relatives of other persons given access to the child support enforcement services of this Article, of his legal obligation to support and shall request such information concerning his financial status as may be necessary to determine whether he is financially able to provide such support, in whole or in part. In cases involving a child born out of wedlock, the notification shall include a statement that the responsible relative has been named as the biological father of the child identified in the notification.
In the case of applicants, the notification shall be sent as soon as practical after the filing of the application. In the case of recipients, the notice shall be sent at such time as may be established by rule of the Illinois Department.
The notice shall be accompanied by the forms or questionnaires provided in Section 10-5. It shall inform the relative that he may be liable for reimbursement of any support furnished from public aid funds prior to determination of the relative's financial circumstances, as well as for future support. In the alternative, when support is sought on behalf of applicants for or recipients of financial aid under Article IV of this Code and other persons who are given access to the child support enforcement services of this Article as provided in Section 10-1, the notice shall inform the relative that the relative may be required to pay support for a period before the date an administrative support order is entered, as well as future support.
Neither the mailing nor receipt of such notice shall be deemed a jurisdictional requirement for the subsequent exercise of the investigative procedures undertaken by an administrative enforcement unit or the entry of any order or determination of paternity or support or reimbursement by the administrative enforcement unit; except that notice shall be served by certified mail addressed to the responsible relative at his or her last known address, return receipt requested, or by a person who is licensed or registered as a private detective under the Private Detective, Private Alarm, Private Security, Fingerprint Vendor, and Locksmith Act of 2004 or by a registered employee of a private detective agency certified under that Act, or in counties with a population of less than 2,000,000 by any method provided by law for service of summons, in cases where a determination of paternity or support by default is sought on behalf of applicants for or recipients of financial aid under Article IV of this Act and other persons who are given access to the child support enforcement services of this Article as provided in Section 10-1.
305 ILCS 5/10-4