Illinois Child Support Policy 2024-2026

Illinois law under 750 ILCS 5/505(a)(3.8) establishes that when a parent has the child for at least 146 overnights per year (equivalent to 40% of the year), they are considered to have "shared physical care." This threshold triggers a fundamentally different calculation method that uses a 1.5x multiplier on the basic child support obligation. The rationale is that maintaining two separate households for a child creates duplicated fixed costs—rent, utilities, furniture, supplies—that don't exist when one parent has the majority of time. The 1.5x multiplier increases total available support to account for these dual-household expenses.

Illinois offers two methods to calculate net income under 750 ILCS 5/505(a)(3): (1) Standardized Method: Use the state-published gross-to-net income conversion table based on gross income and number of exemptions. This simplified approach assumes standard tax withholdings and FICA deductions. (2) Individualized Method: Itemize specific allowable deductions from gross income including federal/state income taxes, FICA/Medicare, mandatory retirement, union dues, health insurance premiums, court-ordered support for others, and necessary business debt repayment. The individualized method provides more accuracy for self-employed individuals or those with non-standard deductions.

When both parents meet the 146-overnight threshold, Illinois applies a multi-step shared care formula: (1) Multiply the basic child support obligation (BCSO) by 1.5 to create the shared care obligation. (2) Apportion this grossed amount between parents based on their income shares. (3) Calculate each parent's overnight percentage (overnights ÷ 365). (4) Cross-multiply: multiply each parent's apportioned obligation by the OTHER parent's overnight percentage. This determines what each owes to support the child during the other parent's time. (5) Offset the two amounts—the parent with the higher obligation pays the difference to the other parent.

Under 750 ILCS 5/505(a)(4), three categories of expenses are handled separately and added to the basic support obligation: (1) the marginal cost of health, dental, and vision insurance premiums specifically for the children, (2) work-related childcare costs necessary for employment or education/training, and (3) extraordinary expenses like private school tuition or special medical needs costs (if court-approved). These add-on costs are prorated between parents based on their income shares. The parent who pays them directly receives credit, and the final support payment is adjusted accordingly.

Illinois defines gross income very broadly under 750 ILCS 5/505(a)(3) as "total income from all sources." Includable sources: wages, salaries, bonuses, commissions, self-employment income, investment income (interest, dividends), rental income, pension/retirement payments, Social Security benefits, unemployment benefits, workers' compensation, disability benefits, and spousal maintenance received from another relationship. The only statutory exclusions are means-tested public assistance benefits: Temporary Assistance for Needy Families (TANF), Supplemental Nutrition Assistance Program (SNAP), and Supplemental Security Income (SSI).

Yes, Illinois courts may deviate from guideline amounts under 750 ILCS 5/505(a)(2) if the presumptive amount would be inequitable, unjust, or inappropriate. Common grounds for deviation include: children with special medical, educational, or developmental needs requiring extraordinary expenses; significant disparity in parental resources beyond basic income; a parent's financial resources from non-income sources (e.g., substantial assets); agreements of the parents to a different amount; or circumstances where applying the guideline would create an undue financial hardship. Any deviation requires specific written findings explaining why the guideline amount is inappropriate.