Illinois Child Support: What the Number Does—and Does Not—Cover

The short answer

What Illinois families should know.

Illinois uses an income-shares approach, not a flat percentage of only one parent's paycheck. The basic obligation starts with both parents' incomes and the number of children, then applies statutory adjustments. Childcare, insurance, medical, activity, and educational expenses may be addressed in addition to basic support.

Both parents' incomes are part of the model

The calculation uses statutory net income, which is not always the number shown as take-home pay on one paycheck. Bonuses, commissions, business income, recurring benefits, prior support duties, and statutory deductions may require closer review.

Parenting time can change the calculation

Illinois has a shared-parenting calculation when the statutory parenting-time threshold is met. Equal time does not automatically mean zero support because the parents' incomes and the full formula still matter.

Basic support is not the entire child budget

The judgment may separately allocate work-related childcare, health-insurance premiums, uninsured medical costs, extracurricular activities, school expenses, and later college contributions. Clear reimbursement procedures are essential.

Support does not usually change by itself

A job change, raise, reduction, or changed schedule may support modification, but the existing order remains enforceable until changed through a valid agreement or court order. Waiting can affect retroactivity and arrearages.

Prepare

Useful next steps

Collect complete income records for both parents and identify variable compensation.
Calculate actual overnights from the proposed or existing schedule.
List insurance, childcare, medical, activity, school, and other recurring child expenses.

Avoid

Common missteps

Using gross pay from one statement without statutory adjustments
Assuming equal parenting time eliminates support
Stopping or reducing payments without an enforceable change

Frequently asked questions

Clear answers to the first questions.

Does child support cover extracurricular activities?

They may be allocated in addition to basic support. The order should identify consent, percentages, documentation, caps if any, and reimbursement timing.

Can child support be modified?

Yes, when statutory requirements are met. The correct filing date can matter because modifications are not freely retroactive to any date a parent chooses.

Does child support end automatically at age 18?

Not always. Graduation, age, disability, arrearages, and non-minor educational expenses may require review of the statute and the specific order.

Related Illinois family-law guides.

Primary sources

Read the governing Illinois materials.

This article provides general information and is not legal advice. Laws, court rules, local procedures, and individual facts can change the analysis. Reading it or contacting the firm does not create an attorney-client relationship.