Ill. Admin. Code tit. 89, § 1200.150
a) In order to receive reimbursement by DSCC for covered supports and services and diagnostic services rendered to an applicant or recipient child, a provider shall:
4) Have a provider agreement on file with DSCC;
9) Comply with the applicable requirements of Section 1200.50.
b) DSCC shall be the payer of last resort for covered supports and services and diagnostic services. Payment shall not be made until insurance or any other third party payer has paid or rejected the claim.