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Child Support 101

Like a car engine, child support determination in Illinois is often a mechanical process, but not everyone understands how a car engine runs.  Although I am the son of a mechanic, I know very little about cars.  In the same way, not everyone understands how child support is calculated in Illinois.  The purpose of this short article is to cover the basics of child support calculation and answer some frequent questions about the topic.

The calculation of child support is determined by Illinois statute (750 ILCS 5/505).  The statute provides that the amount of child support a noncustodial parent (payor) pays is to be based on “net income.”  The determination of net income starts with gross income.

Gross Income

Gross income is all of the income a party receives from any sources.  This means more than just a person’s base income from employment.  Gross income means a person’s base income (either salary or hourly compensation), overtime, bonuses, commissions, etc.  Gross income can also include other things such as rental income, regular gifts of cash from parents, and employer perks such as mileage reimbursement or car allowance.

Net Income

The determination of “net income” is made by the court considering the payor’s gross income and subtracting out certain deductions provided by statute, including 1) federal income taxes, 2) state income taxes, 3) FICA taxes, 4) union dues, 5) mandatory pension payments, 6) health insurance premiums and court ordered life insurance premiums and7) any previously ordered support obligations.  From this net income, the payor pays support based on the following set percentages provided in the statute:

       Number of Children             Percent of Net Income
                 1                                         20%                                     
                 2                                         28% 
                 3                                         32% 
                 4                                         40%       
                 5                                         45%          
                 6 or more                                 50%

While the statute allows the court to deviate from these statutory guidelines, the majority of cases in which child support is awarded are based on these statutory guidelines. A discussion of the circumstances in which deviations may be allowed occur is a topic for another time and will not be addressed in this article.

Particular Challenges

Sometimes, gross income fluctuates. For instance, a payor’s gross income may vary due to the amount of hours worked, overtime, bonuses, commissions or other factors. In those situations, a court may require special language in the child support order. The order may require regular payments of child support based on the payor’s base pay and also require a payor to make support payments on any bonuses and other periodic sources of income from time to time, if and when received.

Sometimes a non-custodial parent has no reported income. While these cases are always more difficult, there are ways of establishing the non-custodial parent’s income. Establishing income when no income is reported involves some investigation, due diligence and a little common sense. For example, business receipts, bank deposits, and other documentation can help establish the actual income. Another way of determining income is to look at what is listed as income when the non-custodial parent applied for credit, such as a credit card or home loan. A third method is to look at non-custodial parent’s standard of that can be revealed in a budget affidavit and/or examining canceled checks, checks ledgers, bank account and other documentation of business and lifestyle expenses.

These and other tactics by a creative and experienced attorney are often used. It would be hard to believe a person has no income when they are paying $1,200 per month in rent or mortgage payments, have a car payment and eat out every night. If a judge sees evidence of an attempt to hide income or failure to be forthright, the uncertainties are usually resolved against the non-custodial parent who is not being open and honest. The judge will make a determination of income and child support, even if the non-custodial parent does not supply the figures and documentation to back them up.

A New Spouse’s Income

If a non-custodial parent remarries, the new spouse’s income is not generally considered as part of the child support equation. A new spouse’s income does not have a direct effect on the child support obligation; however, a new spouse’s income may have an indirect effect. A change in the amount of income taxes paid by the non-custodial parent can change the support calculation. The income of a non-custodial parent’s spouse may also impact other related support matters that are focused more on the ability to pay, such as contributions to uncovered medical expenses, daycare costs, extra-curricular activity expenses and college expenses.


While the amount of child support will ultimately be determined by the court, a person can estimate the amount of support likely to be determined by following the direction of 750 ILCS 5/505 and going through the process outlined in the statute. Some law libraries provide child support calculators that can be accessed online. Of course, there is no substitute for the assistance of a knowledgeable, experienced family law attorney, who can evaluate the situation, taking into account any nuances and factors a layperson might overlook. Allow specific circumstances sometimes require some analysis, the law in Illinois sets a fairly strict framework for the determination of child support that is understandable and which is straightforward to apply in most situations.


Roman J. Seckel
Drendel & Jansons Law Group
111 Flinn Street
Batavia, Il 60510
[email protected]

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The Drendel & Jansons Law Group practices law in Illinois, and the discussion in this article presumes the application of Illinois law. The principles and opinions expressed are general in nature and are not intended as specific legal advice applicable to specific situations. No interaction in regard to this article is intended to establish an attorney/client relationship.