Illinois child support guidelines

How does Illinois calculate child support?

Illinois uses the income shares guideline under 750 ILCS 5/505, with the statutory edition dated July 1, 2017, confirmed on October 15, 2026. The Illinois Department of Healthcare and Family Services updated its income conversion table and schedule amounts effective March 20, 2026. The schedule uses combined monthly net income and the number of children, rather than a flat percentage of one parent’s income.

Gross income generally includes income from all sources, excluding means-tested public assistance and benefits or income received for other children in the household. Net income subtracts the standardized tax amount, or an eligible individualized tax amount, and statutory adjustments. Tax deductions account for federal and state income taxes, Social Security and Medicare, with applicable alternatives for self-employment tax or mandatory retirement contributions. These income rules come from 750 ILCS 5/505.

The worksheet adds each parent’s monthly net income, selects the scheduled basic obligation, and assigns each parent a share proportional to income under 750 ILCS 5/505. The receiving parent’s share is presumed spent directly on the child, not paid to the other parent. Above the schedule’s highest income level, the court has discretion, but the basic obligation cannot fall below the obligation at the schedule’s highest level.

• Low-income minimum: a rebuttable presumption—one the court can find does not apply—provides for $40 a month per child, capped at $120 a month across the paying parent’s children (750 ILCS 5/505).
• A zero-dollar order is presumed for parents with no gross income, only means-tested assistance, or inability to work because of medically proven disability, incarceration, or institutionalization (750 ILCS 5/505).

How does shared parenting time change support?

When each parent has at least 146 overnights a year, the basic obligation is multiplied by 1.5 under 750 ILCS 5/505. Each parent receives a share of that shared-care obligation based on their percentage of combined net income. Each share is then multiplied by the percentage of time the child spends with the other parent.

The resulting obligations are offset, and the parent owing more pays the difference. Equal parenting time therefore does not automatically mean no support. The agency provides a Shared Physical Care Support Obligation Worksheet; the parenting time calculator can help organize an overnight count.

What else changes the Illinois amount?

Expenses and income adjustments can change the result under 750 ILCS 5/505. A court may also depart from the guideline if applying it would be inequitable, unjust, or inappropriate, but must give written reasons and state the guideline amount.

• Child care: reasonable costs needed for employment, training, or a job search may be divided in proportion to net income. An allowed federal child care tax credit reduces the cost used.
• Health insurance: the actual premium attributable to the child is added to the basic obligation.
• Uninsured care: basic ordinary out-of-pocket medical expenses are partly covered by the basic obligation. A court may order contributions toward additional reasonable uninsured health care.
• Other children with an order: support actually paid is deducted from net income unless the court finds economic hardship to the child.
• Other children without an order: the deduction is actual support paid or 75% of the guideline support for that child, whichever is less, subject to the hardship exception (750 ILCS 5/505).
• Departure reasons may include extraordinary medical expenditures needed to preserve life or health and additional expenses for a child.

When does support end or change?

The order must state a termination date no earlier than age 18 under 750 ILCS 5/505. If high school continues after age 18, that date cannot be earlier than graduation or age 19, whichever comes first. The termination date does not erase unpaid support.

For child care expenses, 750 ILCS 5/505 expressly permits modification upon a substantial change in circumstances. A new calculator result alone does not change an existing order. The Illinois Department of Healthcare and Family Services, Child Support Services provides an official guideline calculator and worksheets for checking the calculation; its official links appear on this page.