Illinois uses the Income Shares model to calculate child support, which means both parents' incomes are combined, and each parent's share of child support is based on their proportion of the combined income.
Under the Income Shares model, the court looks at what both parents earn together. A guideline table then determines the total child support obligation based on combined income and the number of children. Each parent is responsible for their proportional share. For example, if one parent earns 60% of the combined income, they are responsible for 60% of the child support obligation. The non-custodial parent typically pays their share to the custodial parent.
The Illinois child support guidelines provide specific tables and formulas that courts use to determine the appropriate amount. Judges can deviate from these guidelines in special circumstances, but the calculated amount is the presumptive starting point.
For the official guidelines, visit the Illinois child support guidelines.
Income for child support typically includes wages, salary, bonuses, commissions, self-employment income, rental income, investment returns, retirement payments, Social Security benefits, disability payments, and trust distributions.
Importantly, courts in Illinois can look beyond what appears on a tax return. If a parent is self-employed or owns a business, the court can examine business records, bank statements, and lifestyle evidence to determine true income. Personal expenses paid by a business, unreported cash income, and excessive business deductions can all be added back as income for child support purposes.
Read our complete guide to what counts as income →
In Illinois, you can request a modification of child support when there has been a material change in circumstances. This typically includes:
To file a modification in Illinois:
The Illinois Department of Healthcare and Family Services can help with modification requests. Visit their website at Illinois Department of Healthcare and Family Services.
Read our step-by-step modification guide →
Official Illinois child support calculation guidelines and tables.
State agency that handles child support enforcement and services.
Search Illinois business registrations and filings.
Learn what evidence Illinois courts accept for proving hidden income.
Find business filings and property records that may reveal hidden income.
This information is for educational purposes only and is not legal advice. Child support laws in Illinois may change. Consult a licensed Illinois attorney for advice specific to your situation.