750 ILCS 5/505 Explained: The Illinois Child Support Statute

What Section 505 covers

Section 505 of the Illinois Marriage and Dissolution of Marriage Act, cited as 750 ILCS 5/505, is the Illinois child support statute. It applies in divorce, legal separation, invalidity and civil union cases, and in modification, temporary relief and parental responsibility proceedings (505(a)). A "child" is anyone under 18, and anyone 18 or older who has not reached 19 and is still in high school. The Illinois Department of Healthcare and Family Services (HFS) adopts the guidelines, worksheets and the schedule of basic child support obligations (505(a)(1)).

The ilga.gov page shows the current text and the text as amended by Public Act 104-0733, effective January 1, 2027; the changes are noted below. See also our guide to the Illinois Marriage and Dissolution of Marriage Act and, for spousal support, the Illinois maintenance calculator.

505(a)(1.5): computing the basic obligation

Under 505(a)(1.5), the court computes the basic obligation in four steps:

1. Determine each parent's monthly net income.
2. Add them to get the combined monthly net income.
3. Select the amount on the HFS schedule for that combined income and the number of children.
4. Calculate each parent's percentage share of that amount.

The receiving parent's share is presumed spent directly on the child. So if one parent has 60% of the combined net income and the child lives mainly with the other parent, the first parent pays 60% of the schedule amount, before adjustments. HFS calls this the Income Shares Guideline Model.

505(a)(2) and (3.3): the guideline presumption

The court applies the guidelines unless it finds them inappropriate after considering the child's best interests and factors such as the child's and parents' resources and needs, the standard of living the child would have had, and the child's physical, emotional and educational needs (505(a)(2)). The guideline amount is presumed correct, a presumption that can be rebutted (505(a)(3.3)).

505(a)(3): income and net income

Gross income is income from all sources (505(a)(3)(A)), except means-tested public assistance, such as TANF, SSI and SNAP, and benefits received for other children in the household. Social Security disability or retirement benefits paid for the child count as income of the disabled or retired parent, who receives a credit for them. Taxable court-ordered maintenance counts in the recipient's gross income.

Net income is gross income minus a tax amount and certain adjustments (505(a)(3)(B)). The default is the standardized tax amount: federal and state income tax for a single person claiming the standard deduction, one personal exemption and the children's dependency exemptions, plus Social Security and Medicare tax. HFS publishes the conversion table (505(a)(3)(C)). An individualized tax amount can be used when the parties agree or the court determines one under 505(a)(3)(E). See how to fill out an Illinois financial affidavit.

Adjustments (505(a)(3)(F)) include a deduction for a parent who supports a child not shared with the other parent (support actually paid under an order or, without one, the lesser of support actually paid or 75% of the guideline amount, unless that causes the child economic hardship) and a deduction for court-ordered maintenance.

505(a)(3.1) and (3.2): business and potential income

Business income (3.1). Net business income is gross receipts minus ordinary and necessary business expenses. The accelerated part of depreciation and any expense found inappropriate or excessive is not deducted, and perks such as a company car or free housing count as income if they are significant and reduce personal expenses.

Potential income (3.2a and 3.2b). If a parent is voluntarily unemployed or underemployed, support is based on potential income, considering factors such as the parent's assets, work history, skills, education, health and the local job market. With too little work history, potential income is presumed to be 75% of the most recent federal poverty guideline for one person, a presumption that can be rebutted. Incarceration is not voluntary unemployment. A court may impute income only after an evidentiary hearing or by agreement, with specific written findings.

The HFS schedule, minimum orders and high incomes

According to the HFS income shares page, Illinois updates the schedule and the gross to net income table each year, and the latest amounts took effect March 20, 2026. Our guide to Illinois child support in 2026 and 2027 explains which materials apply when.

• Above the schedule (3.5). If combined adjusted net income exceeds the highest level of the schedule, the court may use its discretion, but the basic obligation may not be less than the amount at that highest level.
• Minimum order (3.3a). There is a rebuttable presumption of a minimum order of $40 per month per child, up to $120 per month in total, for a parent whose actual or imputed gross income is at or below 75% of the most recent federal poverty guideline for one person. From January 1, 2027, the threshold is 100% of the guideline.
• Zero-dollar order (3.3b). For a parent with no gross income, who receives only means-tested assistance, or who cannot work because of a medically proven disability, incarceration or institutionalization, a zero-dollar order is presumed instead.

505(a)(3.8): shared physical care, now and in 2027

Through December 31, 2026. Shared physical care applies when each parent has 146 or more overnights a year with the child (505(a)(3.8)). The basic obligation is multiplied by 1.5, each parent's income share of that amount is multiplied by the percentage of time the child spends with the other parent, and the two results are offset; the parent who owes more pays the difference.

Beginning January 1, 2027. Under Public Act 104-0733:

• Shared physical care means each parent has 110 or more overnights a year, or 110 or more overnight equivalents determined by a court as a deviation from the guidelines or agreed by the parties. Overnight equivalents count significant periods of direct care on separate days when the child does not stay overnight.
• The 1.5 multiplier and the offset remain.
• A parent with fewer than 146 overnights or equivalents has that parent's shared care obligation increased by the percentage in the table below, but not above the amount the basic guidelines would produce.

Split physical care (3.9). When each parent has physical care of at least one, but not all, of the children, support is figured on two worksheets and the smaller amount is subtracted from the larger.

For parenting plans, see co-parenting vs parallel parenting in Illinois.

Deviations and added costs

Deviations (3.4). The court may depart from the guidelines if applying them would be inequitable, unjust or inappropriate, with written findings that state the reasons and the guideline amount. Reasons can include extraordinary medical expenses needed to preserve the life or health of a parent or child, a child's special medical, physical or developmental needs, or another factor the court finds appropriate after considering the child's best interest.

Added costs. In addition to the basic obligation, the court may order the parents to contribute to:

• reasonable school and extracurricular expenses (3.6);
• reasonable child care that lets a parent work, attend school or training, or look for work, prorated by each parent's share of combined net income, with notice of a change in cost within 14 days (3.7); and
• health care. The court must provide for the child's current and future medical needs, for example through health insurance; the child's share of the premium is added to the obligation, and uncovered health costs may be divided (4).

The court may also require reasonably affordable life insurance to secure support (505(a-3)).

Modifying, enforcing and ending support

Modification (750 ILCS 5/510). A support order can be modified only for installments that come due after notice of the motion to modify. Child support can be modified on a showing of a substantial change in circumstances. It can also be modified without one to provide for the child's health care needs or, in cases receiving HFS child support enforcement services, when the guideline amount differs from the order by at least 20% and at least $10 a month and at least 36 months have passed since the order was entered or last modified. Section 510 as amended by Public Act 104-0733 (enacted; effective January 1, 2027) lets a court apply later changes to Section 505 to an existing order only if it finds a substantial change in circumstances that warrants applying them; a new Public Act alone is not such a change unless it expressly says so. It also adds a modification ground for a parent incarcerated, or released after incarceration, for more than 180 consecutive days. See how to modify child support in Illinois.

Enforcement (505(b) and (d)). Failure to pay is punishable as contempt, with possible probation or periodic imprisonment of up to 6 months, and a court may suspend the Illinois driving privileges of a parent 90 days or more behind. Each unpaid installment is a judgment, overdue support is a lien on the obligor's property, and unpaid support accrues simple interest. See how to enforce a child support order and the petition for rule to show cause in Cook County.

End date and income updates (505(g) and (h)). The order states a termination date no earlier than the child's 18th birthday or, for a child still in high school at 18, no earlier than the earlier of graduation or the 19th birthday; the date does not cancel unpaid arrears. Beginning January 1, 2027, support orders must also require both parents to exchange written information verifying net income every year. See when child support ends in Illinois.

How Chicago Family Attorneys can help

Chicago Family Attorneys handles child support matters for parents in Chicago and Cook, DuPage, Lake and Will Counties, from its office in Chicago. See the firm's Chicago child support lawyer page.

• Full representation: an initial payment of $1,500 to $2,500, then $500 to $650 per month beginning 30 days after the initial payment while representation remains active.
• Limited scope: drafting from $500 and one hearing appearance from $1,200.
• Court order enforcement: an individually quoted upfront amount plus $350 per hour.

See child support fees and court order enforcement fees. Fees are confirmed in writing before you engage the firm, and no lawyer can promise a particular result. Consultations are by phone; a free weekend consultation is available by Zoom. Call 312-965-5618.