Illinois child support is set by a formula based on both parents' income, and the state enforces collection through wage withholding and tax intercept

In Illinois, child support is calculated using the Income Shares Model, which means the court looks at both parents' gross income and divides the support obligation based on each parent's share of the total household income. The state does not use a flat percentage; instead, a judge or administrative officer applies a statutory formula that accounts for how much time each parent spends with the child, health insurance costs, and childcare expenses. Once an order is in place, the Illinois Department of Financial and Professional Regulation (IDFPR) and the state's child support enforcement agency collect payments, usually by taking money directly from the paying parent's paycheck.

The process starts when one parent files a petition in the circuit court of the county where the child lives, or where the other parent lives. If both parents agree on the amount, they can submit a written agreement to the judge, who will review it for reasonableness. If they disagree, a hearing is held, and the judge decides. Once the order is signed, it becomes enforceable immediately, even if either parent appeals.

Key Takeaways

  • Illinois calculates child support using both parents' gross income, not a simple percentage, and the amount changes if either parent's income changes significantly.
  • The paying parent's employer is ordered to withhold child support from their paycheck automatically, and the state sends the money to the receiving parent or a state disbursement unit.
  • A parent can request a modification if income drops by 10 percent or more, or if there is a substantial change in custody or childcare costs.
  • If a parent falls behind on payments, the state can intercept tax refunds, suspend driver's licenses, and report the debt to credit bureaus.

How the Illinois child support formula calculates the amount

The court starts by adding both parents' gross monthly income—wages, self-employment income, bonuses, rental income, and certain benefits. Illinois law sets a cap on combined parental income used in the formula; as of the most recent statutory update, this cap exists but the exact dollar amount changes periodically, so you will need to check the current Illinois Compiled Statutes Section 750 ILCS 5/505 or ask the court clerk for the current figure.

Once total income is determined, the court applies a percentage based on the number of children. For one child, the guideline is roughly 20 percent of combined income; for two children, roughly 32 percent; for three, roughly 40 percent; for four, roughly 45 percent; and for five or more, roughly 50 percent. These are guidelines, not absolute rules—a judge can deviate if the guideline amount would be unjust or inappropriate given the parents' circumstances, the child's needs, or either parent's ability to pay.

The calculated amount is then split between the parents based on their income ratio. If one parent earns 60 percent of the combined income and the other earns 40 percent, the first parent pays 60 percent of the guideline obligation. The court also factors in the amount of time each parent spends with the child; if one parent has the child more than 40 percent of the time, the formula adjusts downward for the paying parent. Health insurance premiums, childcare costs, and other children from other relationships can also reduce the amount owed.

Income sources the court includes and excludes

The court counts most forms of income: W-2 wages, self-employment earnings, rental income, interest and dividend income, Social Security benefits (except Supplemental Security Income), unemployment benefits, workers' compensation, and military allowances. If a parent is voluntarily unemployed or underemployed—meaning they could earn more but choose not to—the court may "impute" income, or assume they are earning at a higher level, and calculate support based on that assumed income.

The court does not count Supplemental Security Income (SSI), Temporary Assistance for Needy Families (TANF), food stamps, or housing assistance. Child support received for other children is also excluded from income. If a parent is in school full-time or caring for a very young child, the court may consider that when deciding whether to impute income, but it is not automatic.

How payments are collected and where the money goes

Once a child support order is entered, the court sends it to the paying parent's employer with an Income Withholding Order. The employer must begin withholding the amount from the employee's paycheck within a set timeframe—usually within two pay periods. The withheld money goes to the State Disbursement Unit (SDU), a centralized payment processor run by the state. The SDU then forwards the payment to the receiving parent, either by check, direct deposit, or a prepaid debit card, depending on the receiving parent's choice.

If the paying parent is self-employed or does not have a regular employer, they must make payments directly to the SDU or to the receiving parent, depending on the order. Payments are due on the date specified in the order, usually the first or fifteenth of the month. If a payment is late, it accrues as arrears (back-owed support) and can trigger enforcement action.

The receiving parent does not have to do anything to receive the payment once the order is in place and withholding is set up. If the paying parent changes jobs, the state's child support enforcement agency is supposed to locate the new employer and send a new withholding order, though this can take time. The receiving parent can contact the local child support enforcement office to report a job change if they become aware of it.

Modifying the child support amount

Either parent can request a modification if there has been a substantial change in circumstances. Illinois law defines this as a change in either parent's income of 10 percent or more, a significant change in custody or parenting time, a change in health insurance costs, or a change in childcare expenses. The parent requesting the modification must file a petition in the same court that issued the original order.

The modification process is similar to the original hearing: both parents submit income documentation, and a judge reviews the evidence and decides whether to change the amount. Modifications are effective from the date the petition is filed, not from the date the judge signs the new order, so it is important to file promptly if circumstances change. If a parent's income drops significantly—for example, due to job loss—they should file immediately, because they remain responsible for the old amount until a new order is entered.

A parent cannot simply stop paying while waiting for a modification hearing. If they do, arrears accumulate, and the state can pursue enforcement. However, if a modification is granted retroactively, the court may adjust or forgive some of the arrears owed during the period between the change in circumstances and the new order.

Enforcement actions when payments are missed

If the paying parent falls behind, the state's child support enforcement agency has several tools. The most common is tax intercept: the state notifies the federal government that the parent owes child support, and any federal tax refund is seized and applied to the debt. The state can also intercept state tax refunds. This process is automatic once arrears reach a certain threshold, usually $150 or more.

The state can also suspend the paying parent's driver's license, professional license, or recreational license (such as a hunting or fishing license). A notice is sent before suspension, and the parent can request a hearing to contest it. If the parent is in arrears and does not respond to notices, the state can file a contempt of court motion, which can result in jail time, though jail is typically a last resort and is meant to coerce payment, not punish.

The state reports child support arrears to credit bureaus, which damages the paying parent's credit score. The state can also place a lien on property, garnish bank accounts, or pursue other collection methods. None of these actions require a separate court order; they are part of the enforcement agency's standard collection toolkit once an arrearage exists.

What happens if a parent moves out of state

Illinois is part of the Uniform Interstate Family Support Act (UIFSA), which allows the state to enforce child support orders across state lines. If the paying parent moves to another state, the receiving parent can ask the Illinois child support enforcement agency to send the order to the other state's enforcement agency, which will then pursue collection in that state. The receiving parent does not have to file a new case; the existing Illinois order remains valid.

If the paying parent moves and stops paying, the state can still intercept tax refunds, suspend licenses, and pursue other enforcement. However, if the paying parent moves to a state with different income levels or cost of living, either parent can request a modification based on the new circumstances. The case can be transferred to the other state's court system, or it can remain in Illinois—this depends on where the child lives and which state has jurisdiction.

Frequently Asked Questions

Can child support be ordered if the parents were never married?

Yes. In Illinois, a child support order can be entered whether or not the parents were married. If paternity has not been established, the court will address that first, usually through a genetic test or an acknowledgment of paternity signed by both parents. Once paternity is established, the child support calculation proceeds the same way as in a divorce case.

What if the paying parent loses their job?

The paying parent must file a modification petition immediately. They remain responsible for the old amount until a new order is entered, so arrears will accumulate if they do not pay. However, if they file promptly and can show the job loss was involuntary, a judge may reduce or suspend the obligation while they search for work. They must also show they are making a good-faith effort to find employment.

Can child support be enforced after the child turns 18?

In Illinois, child support typically ends when the child turns 18 or graduates from high school, whichever is later. However, if the child is still in high school after turning 18, support continues until graduation or age 19, whichever comes first. Support does not automatically extend to college. Arrears owed before the child turns 18 can still be collected after that date.

How do I report a parent who is not paying child support?

Contact your local child support enforcement office, which is usually part of the county's Department of Human Services or a similar agency. You can also call the Illinois Department of Financial and Professional Regulation's child support hotline or visit their website. Have the paying parent's name, Social Security number, and last known employer information ready. The state will then pursue collection on your behalf at no cost to you.

Can child support be waived or forgiven?

Only a judge can waive or reduce child support, and only if both parents agree or if the judge finds good cause. A parent cannot simply decide to forgive the debt on their own. If the receiving parent wants to reduce or stop support, they must file a modification petition and appear before a judge. Any agreement between the parents must be approved by the court to be enforceable.