Below we provide the Illinois child support office phone number and online website. The Child Support Enforcement agency in Illinois can help you establish and enforce a child support order as well as help establish paternity, collect unpaid child support payments and locate non-custodial parents. If you are looking to collect child support payments then contact the child support office in IL below, where you can file a complaint. The age of emancipation in Illinois is 18. Please note this site is for informational purposes only, do not use for legal advice.