ILLINOIS SUPPORT GUIDELINE
Illinois child support calculator & worksheet
The Illinois child support calculator uses the income-shares schedule to estimate basic support from both parents’ monthly net income. This guide explains the inputs and links to the printable worksheet and official HFS tables. Shared physical care, add-on expenses and gross-to-net conversion require the full worksheet.
Current module status
| State | Illinois |
|---|---|
| Status | Active base worksheet module |
| Guideline model | income shares monthly table |
| Primary income field | Combined monthly net income |
How Illinois child support law works
Legal starting point. Illinois uses an income-shares model in 750 ILCS 5/505. The state annually publishes the conversion and schedule materials that turn the parents’ income information into a combined basic-support obligation. Read 750 ILCS 5/505(a).
How the guideline is calculated
The calculation identifies each parent’s net income, selects the schedule amount for their combined monthly net income and child count, then allocates it by percentage. Shared physical care, child care, insurance, extracurricular costs, other families, and deviations need the full worksheet.
What this site’s worksheet covers
Uses the Illinois HFS 2026 Income Shares Schedule of Basic Child Support Obligations based on net income, effective March 20, 2026. The HFS income-shares page states Illinois annually updates both the Gross to Net Income Conversion Table and the Income Shares Schedule, and the schedule was most recently revised effective March 20, 2026. This base module allocates the schedule obligation by each parent’s share of combined monthly net income. Standardized gross-to-net conversion, health insurance, child care, extracurricular expenses, shared physical care, multi-family adjustments and deviations require the full Illinois worksheet. The HFS 2026 schedule stops at $27,374.99 combined monthly net income. Above that row this module shows no amount, because Illinois applies its high-income analysis. Use the official worksheet.
Documents that make the worksheet more useful
Illinois income shares worksheet; standardized or individualized tax determination. Gather the records that support the income, parenting-time, insurance, child-care, and other adjustment entries that apply to the family. The calculator applies the guideline formula described above and identifies any listed worksheet line it does not compute.
For a filing or agreement, complete the official court forms linked on this page. They use the same guideline structure explained here, and the court applies it to the facts of the case.
Before you enter your numbers
Can Illinois use my actual tax withholding?
Illinois distinguishes standardized and individualized tax treatment when determining net income. A payroll deduction does not automatically establish the guideline tax amount. HFS publishes conversion and basic-support tables for the applicable year, and the shared-care calculation is a separate step from finding the table amount.
Prepare this: Keep the table year with your calculation. Identify whether the official worksheet uses standardized or individualized taxes and gather the records that support that choice.
Read the relevant official instructions: Illinois HFS: income shares and annual tables; Illinois Marriage and Dissolution of Marriage Act, section 505(a)(3).
These preparation notes explain one part of the state guideline. A new estimate does not change an existing order; a modification request does.
How Illinois cases actually get to a number
Convert each parent’s income to net using the current HFS method, combine those nets, select the schedule amount, then allocate by percentage. Shared physical care has its own worksheet path.
Illinois 750 ILCS 5/505 is an income-shares model. HFS publishes the net-income conversion and the schedule that turns combined monthly net income into a basic obligation. That is a different path from neighboring states that use another model, so do not import a table, percentage, or overnight credit from somewhere else.
Parenting time in Illinois
Illinois shared-physical-care calculations are not a simple overnight credit against a sole-care schedule. If the parenting plan meets the shared-care definition, use that worksheet. Otherwise stay on the basic allocation.
Costs Illinois usually treats separately
- Child-care expenses
- Health-insurance premiums for the children
- Extracurricular and extraordinary expenses the court includes
- Support of other children as the statute allows
When Illinois courts leave the guideline
Deviation requires findings. High income above the schedule, a child’s own resources, and medical needs are common issues. Do not invent a percentage above the last schedule row.
Official Illinois forms to keep beside this guide
Illinois income shares worksheet; standardized or individualized tax determination. The calculator applies the guideline formula described above and identifies any listed worksheet line it does not compute. The primary authority is the published Illinois source. Fill the official form from source documents. Use this page only to check that you chose the right Illinois path—primary versus shared, table versus percentage, add-ons versus basic support.
Where this is typically filed
Circuit Court hears family cases; HFS/DCSS handles IV-D. Always use the current year’s schedule and net-income conversion, which HFS updates.
Questions about Illinois child support
How does the Illinois income-shares calculator work?
The basic calculation combines both parents’ monthly net income, selects the schedule obligation for the number of children and allocates it by income share. Net income must be determined under Illinois rules. This site does not perform the standardized gross-to-net conversion or all later worksheet adjustments; check the HFS tables and instructions for those steps.
Official Illinois income-shares tables
Does Chicago or DuPage County use a separate calculator here?
This guide follows the Illinois statewide income-shares rules. A case in Chicago or DuPage County still needs the applicable Illinois worksheet and any court-ordered deviations. This site does not provide a separate county-specific formula. Review the state rules and use the appropriate court forms for the case.
Illinois child-support statute, 750 ILCS 5/505
Does equal parenting time make Illinois child support zero?
Do not assume that equal parenting time eliminates support. Shared physical care has its own calculation, and income differences and additional child-related costs can affect the obligation. This module provides the base schedule allocation; the full Illinois worksheet is needed for shared-care and other case-specific adjustments.
Illinois HFS calculator resources
Which Illinois schedule should I use?
Use the official HFS schedule that applies to the calculation date and check the rule version shown with this site’s result. HFS updates its income-shares and gross-to-net materials; a prior-year search result can lead to a different schedule. Review income limits and the supported scenario before saving a PDF.
Current HFS schedule and conversion tables · Open the Illinois worksheet
Guide wording updated .
Run the calculator
Open the free support calculator, select Illinois, complete the state worksheet, and print or export the output for review.