How Is Child Support Calculated in Illinois?

Child support in Illinois is determined using the

income shares model

, which replaced the previous percentage-of-income method in 2017 to more equitably apportion costs based on both parents’ finances. This approach estimates the total support a child would receive if parents remained intact and divides it proportionally by income shares.

Illinois Child Support Guidelines Overview

Effective July 1, 2017, via Public Act 99-0764, Illinois shifted from a non-custodial parent’s net income percentage to the income shares guideline model. Previously, payments were fixed percentages like 20% for one child or 28% for two, solely from the payor’s income. The new system combines both parents’ adjusted net incomes, applies a basic obligation from official schedules, and allocates shares proportionally.

Statutes governing this are in 750 ILCS 5/505, ensuring consistency across courts unless deviations are justified. Judges typically follow guidelines but may adjust for special needs or extraordinary circumstances.

Step-by-Step: How to Calculate Child Support in Illinois

The calculation follows a structured process using parents’ financial data.

1. Determine Each Parent’s Gross Income: Include wages, salaries, bonuses, commissions, investments, rentals, and other earnings.
2. Calculate Net Income: Subtract allowable deductions like federal/state taxes, union dues, prior child support, spousal maintenance, and health insurance premiums.
3. Combine Net Incomes: Add both parents’ net incomes for total adjusted income.
4. Find Basic Child Support Obligation: Use Illinois Department of Healthcare and Family Services (HFS) schedules based on combined income and number of children.
5. Calculate Income Shares: Each parent’s percentage = (their net income / combined net income) × 100.
6. Allocate Obligation: Multiply basic obligation by each parent’s share. The higher-earning parent typically pays the difference to the custodial parent.
7. Adjust for Additional Factors: Add shares for medical, education, or parenting time if applicable.

Example Calculation

Parents A ($4,000 net/month) and B ($2,500 net/month); combined $6,500; two children. Basic obligation: $1,611. A’s share: 61.5% ($990.77); B’s: 38.5% ($620.23). If B has primary custody, A pays $370.54 monthly ($990.77 – $620.23).

Another example: Combined $5,450 net; one child obligation $1,001. 60% earner pays $600.

Illinois Child Support Obligation Schedule

The HFS provides tables for basic obligations up to certain income levels, transitioning to percentages beyond. While exact full schedules require official tools, general pre-2017 percentages (still referenced) were:

• 1 child: 20%
• 2 children: 28%
• 3 children: 32%
• 4 children: 40%
• 5 children: 45%
• 6+ children: 50% of combined income

For $5,000 combined: 1 child = $1,000; 2 = $1,400; 3 = $1,600. Use estimators for precise figures as schedules update.

Net Income: What Counts and Deductions

Gross income encompasses all sources; net income deducts:

• Federal, state, local taxes
• Social Security, Medicare
• Prior child/spousal support
• Mandatory retirement contributions
• Health insurance for child

Non-cash benefits or imputed income may apply if underemployed.

Adjustments and Additional Expenses

Parenting Time (Shared Custody)

Significant parenting time (≥146 overnights/year) reduces obligation via formula accounting for direct costs.

Health Insurance and Medical Costs

Each parent covers their share; netted against support if payer provides coverage.

Education and Extracurriculars

Apportioned by income share; added to basic support.

Deviations from Guidelines

Courts deviate for child’s special needs, extraordinary expenses, or best interests.

Child Support Estimator Tools

Illinois HFS offers a free Child Support Estimator at hfs.illinois.gov, inputting incomes, deductions, children, and parenting time for guideline estimates. Accuracy depends on data entered; actual orders may vary. Third-party calculators exist but official is preferred.

Duration of Child Support Payments

Obligations end at child’s emancipation: age 18 or high school graduation (whichever later), up to 19 if still in school. College not required unless agreed. Earlier termination if child marries, joins military, or becomes self-supporting.

Modifying Child Support Orders

Seek modification via court for substantial income/need changes (e.g., job loss, promotion). File petition; use estimator for proposed amount.

Enforcement and Non-Payment

HFS enforces via wage garnishment, license suspension, liens, or jail. Report changes promptly.

Frequently Asked Questions (FAQs)

What is the income shares model in Illinois child support?

It combines both parents’ net incomes, determines basic obligation from schedules, and prorates by income shares for equitable division.

How do I calculate my net income for child support?

Start with gross; deduct taxes, prior support, maintenance, and child-related insurance/health costs.

Does shared parenting affect child support in Illinois?

Yes, ≥146 overnights/year triggers adjustment reducing the paying parent’s obligation.

Can child support be modified after a court order?

Yes, upon substantial change in circumstances like income shift or child’s needs.

Where can I find the official Illinois child support calculator?

Use the free HFS Child Support Estimator online.

Table: Sample Basic Obligations (Illustrative)

Combined Net Income	1 Child	2 Children	3 Children
$5,000/mo	$1,000	$1,400	$1,600
$6,500/mo	~	$1,611	~
$5,450/mo	$1,001	~	~

Note: Use official schedules/estimator for accuracy; values approximate from examples.