Complete the on-line application for free child support services if you live in Illinois and the dependent child(ren) lives with you. Download and complete Divorce, Child Support, and Maintenance forms from the Illinois Office of the Courts.Calling the Child Support Customer Service Call Center at 1-800-447-4278 (persons using a teletypewriter or TTY device may call 1-800-526-5812); or. In Illinois, there are new statutory guidelines for the court to consider in calculating child support. Use the child support calculator below to estimate your child support and medical support payments. Illinois child support is based on a variety of factors. For more information about going to court including how to fill out and file forms, call or text Illinois Court Help at 833-411-1121 or go to ilcourthelp.gov. Fill out and sign the forms listed below. Make at least three copies of each form. If your parents are separated or divorced, each parent should fill out the calculator with their own information.