How Is Child Support Calculated in Illinois? 

Chicago Child Custody Attorneys

When parents divorce in Illinois, child support is determined by a formula that changed on July 1, 2017, when Public Act 99-764 amended the Illinois Marriage and Dissolution of Marriage Act (IMDMA). Instead of the old method of relying on the net income of the non-custodial parent, there is now an income-share system that holds both parents accountable for child support based on how much they financially contributed to the combined household income while married.

Many factors affect the amount of child support, and each situation is different; so if you are having issues with child support, it pays to seek legal assistance. The compassionate and experienced Illinois family-law attorneys at Wolfe & Stec understand the stresses of divorce and recognize the concerns parents have for the well-being of their children.  We offer a free initial consultation to examine your individual situation and help come up with solutions that are best for you and your family.

Delaying can only make your situation worse, so call or contact us online today.

What Are Child Support Obligations in Illinois?

Illinois parents must support a child until the child turns 18, or until 19 or graduation if the child is still attending high school full-time, or if a child is disabled and not capable of self-support. Judges may also order parents to help with the expenses of a child over 19 who is attending college.

Under the former law, the amount that the parent was required to pay in child support was based on that parent’s income and the number of children involved. The new “income shares” model for calculating Illinois child support bases the total amount of child support which the parents must pay on the combined net income of both parents. Once this number is determined, each parent’s share of the responsibility for providing that amount of child support is calculated.

To calculate child support, the courts consider the following:

    1. Basic Child Support Obligation – The combined value of child support owed by both parents together. This is then divided proportionally between the parents based on their individual contribution to the combined household net income.
    2. Additional Expenses – Other costs, such as child care and medical costs which are added on top of the basic child support obligation.
    3. Parenting Time – The amount of time the child spends with each parent.
    4. In shared physical care situations, where each parent has the child for at least 146 overnights per year, the total child support obligation is multiplied by a factor of 1.5 and the time spent with the child is factored into the calculation. The more time the obligor parent spends with the child, the less that parent’s obligation will be.

Modifying Support

The new law will not automatically change existing child support obligations.  To change them, parents must file a motion to modify child support and show a substantial change in circumstances, such as an increase or decrease in income of 20 percent, or a changes in expenses, geographical location, or health insurance rates. Parents must fill out a Certification of Income and Expenses form (HFS 2782) to verify ability to pay, financial balances, employment status and other information. ‍However, if the old child support obligation differs by more than 20 percent from the new guidelines, child support may be modified without showing this substantial change.

Parents can agree to modify child support and request that the court approve their proposed change.  If the change does not satisfy Illinois law, it must be adjusted.

If parents can’t agree on a modification, a judge will have to determine whether child support should be modified. The parent requesting the change will need to file legal paperwork asking a court to change child support and giving the reasons why.

What to Do If You Can’t Pay the Calculated Child Support in Illinois

1) Modify Your Support Order

If you are having problems making child support payments, you should immediately seek to modify your existing support order in court and ask to have the support amount lowered.  However, you are still responsible for the full amount of back child support.

2) Consider Filing for Bankruptcy

If you file for either Chapter 7 or Chapter 13 bankruptcy, there is an “automatic stay” that stops all foreclosures, garnishments, bank levies, and creditors from harassing you.  However, the automatic stay does not apply to the collection of child support or alimony, so you will continue to be liable for support previously ordered in family court.


Child support laws can be complicated, and you will have to deal with the results for years. If you have questions about child support, you should contact an attorney to be sure your rights are protected. The skilled Illinois family-law attorneys at Wolfe & Stec, Ltd. know the laws, the courts and the system and can guide you through the process.  We represent and advise clients in all types of child custody matters and have a long history of success.

Don’t delay. For a free initial consultation with an experienced and compassionate DuPage County custody lawyer, call or contact us online.

Attorney Natalie Stec

Natalie M. Stec, born and raised in Illinois, and earned her Bachelor of Science from the University of Illinois at Urbana-Champaign. Her practice has been concentrated in significant pre and post decree marital and family law cases; including custody, visitation, support, and paternity matters. She has important criminal defense experience in both misdemeanor and felony cases. She is a very dedicated and passionate litigator. [ Attorney Bio ]