305 ILCS 5/11-18
It is the duty of every applicant and recipient to notify promptly the county department or the supervisor of general assistance, as the case may be, of any change of status with respect to his property, or need, or family composition, amount of income, money contributions and other support, from whatever source, occurring, in the case of an applicant, between the time of his filing an application for financial aid and the issuance of the grant, and, in the case of a recipient, occurring at any time during the period that he receives financial aid.
If an applicant or recipient fails to give prompt notice of changes in his circumstances, and as a result financial aid is given to which he is not entitled, he shall be liable to the county department or to the local governmental unit, as the case may be, for refunding a sum of money up to but not in excess of the entire amount of financial aid provided. Unless the refund is made the amount may be recovered in a civil action.
305 ILCS 5/11-18