# Illinois child support guidelines and income shares

> How Illinois calculates child support under the income shares model, what the 146 overnight rule changes, and when Illinois parents have to pay for college.

Illinois stopped calculating child support as a flat percentage of the paying parent's income on July 1, 2017. What replaced it asks a different question: what would parents at this combined income level normally spend on this many children, and what share of that should each parent carry.

The answer comes out of a table the state publishes, not out of a formula you can do in your head, and that is the single biggest thing to understand about it.

## How is child support calculated in Illinois?

Four steps, set out in [section 505(a)(1.5)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000):

1. Determine each parent's monthly net income
2. Add them together for combined monthly net income
3. Look up the matching amount in the schedule of basic child support obligations for that combined income and that number of children
4. Calculate each parent's percentage share of that basic obligation

A monetary obligation gets computed for both parents, but only one of them writes a check. The receiving parent's share is not payable to the other parent and is presumed to be spent directly on the child.

The [Illinois Department of Healthcare and Family Services](https://hfs.illinois.gov/childsupport/parents/incomeshares.html) publishes the schedule and the conversion table behind it. The 2026 Illinois Schedule of Basic Obligations and the 2026 Gross to Net Income Conversion Table both took effect on March 20, 2026, and Illinois now updates both every year.

## What is net income for Illinois child support?

Gross income minus taxes, and Illinois gives you two ways to compute the tax part.

The default is the **standardized tax amount**: federal and state income taxes for a single person claiming the standard deduction, one personal exemption, and the applicable dependency exemptions for the children, plus Social Security and Medicare at the FICA rate. HFS publishes a conversion table that turns gross income into net using that assumption, and unless somebody opts out, that table is the answer.

The alternative is the **individualized tax amount**, which uses actual federal income tax, actual state income tax, and actual Social Security or self-employment tax and Medicare. You get there three ways: both parties stipulate to a different computation method, a party opts in at a summary hearing on the strength of a served financial affidavit and produced supporting documents, or the court determines it at an evidentiary hearing on the record.

Gross income means all income from all sources, with two carve-outs. It excludes means-tested public assistance such as TANF, SSI and SNAP, and it excludes benefits and income received for other children in the household, including child support, survivor benefits and foster care payments. It includes maintenance treated as taxable to the payee under an order in this or another proceeding.

### How is business income counted for Illinois child support?

Gross receipts minus ordinary and necessary expenses required to carry on the business, and [section 505(a)(3.1)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000) then closes two doors.

The accelerated component of depreciation, and any business expense found judicially or administratively to be inappropriate or excessive, comes out of the expense side. And any reimbursement or in-kind payment a parent receives from the business, including a company car, reimbursed meals, free housing or a housing allowance, counts as income where it is significant in amount and reduces personal expenses.

That is why a self-employed parent's tax return is the beginning of the analysis rather than the end of it. Sorting a genuine business expense from a personal one across three years of statements is the work that decides these cases, and the [financial affidavit chapter](https://www.counselpro.ai/divorce-guide/illinois/financial-affidavit-and-discovery) covers how those records get pulled.

## What if a parent is unemployed or hiding income in Illinois?

The court can impute income, with procedural guardrails. Under section 505(a)(3.2a), if a parent is voluntarily unemployed or underemployed, support is calculated on potential income, and the court considers that parent's assets, ownership of a substantial non-income producing asset, residence, employment and earning history, job skills, education, literacy, age, health, criminal record and other employment barriers, and record of seeking work, plus the local job market and prevailing earnings.

Where there is not enough work history to judge, there is a rebuttable presumption that the parent's potential income is 75 percent of the most recent federal poverty guideline for a household of one. Incarceration is not treated as voluntary unemployment.

Section 505(a)(3.2b) adds the guardrail: income may be imputed only after an evidentiary hearing or by agreement of the parties, and imputation has to be accompanied by specific written findings identifying the basis for it.

## What does 146 overnights do to Illinois child support?

It changes the formula entirely. Under [section 505(a)(3.8)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000), if each parent exercises 146 or more overnights per year with the child, the basic obligation is multiplied by 1.5 to get the shared care obligation. Each parent's share of that is set by their percentage of combined net income. Each parent's share is then multiplied by the percentage of time the child spends with the other parent, and the two results are offset, with the parent owing more paying the difference.

One hundred forty-six overnights is exactly 40 percent of a year. A schedule that lands at 145 and a schedule that lands at 146 produce meaningfully different numbers, which is why parenting time and support end up negotiated together rather than in sequence. The [parenting time chapter](https://www.counselpro.ai/divorce-guide/illinois/parental-responsibilities-and-parenting-time) covers how the schedule itself gets decided.

Split care has its own rule. Where there is more than one child and each parent has physical care of at least one but not all of them, support is worked out on two separate worksheets and offset.

## What gets added on top of Illinois child support?

Three things, and all are discretionary rather than automatic.

- **Child care.** The court may add reasonable child care expenses, prorated by each parent's share of combined net income, with each parent's portion stated separately in the order. Actual costs are used where available, averaged over the most recent 12 months when they vary. The value of the federal child care tax credit is subtracted from the actual cost. A party whose child care costs change has 14 days to notify the other.
- **School and extracurricular expenses.** The court may order either or both parents to contribute to reasonable school and extracurricular costs intended to enhance the child's educational, athletic, social or cultural development.
- **Health care.** Support orders address health insurance and unreimbursed medical costs, and a need to provide for the child's health care needs is itself a ground for modifying an order.

## What if the parents earn more than the schedule covers?

The court gets discretion, with a floor. The published schedule runs up to a combined monthly net income band of $24,475.00 to $24,524.99, where the basic obligation is $3,211 for one child, $4,721 for two, $5,507 for three, $6,151 for four, $6,766 for five and $7,355 for six.

Above that, [section 505(a)(3.5)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000) lets the court use its discretion, except that the basic obligation may not be less than the amount at the highest combined net income level in the schedule. High earners argue about what goes above the floor, not about whether there is one.

At the other end there is a minimum. A rebuttable presumption sets a $40 per month per child obligation for an obligor with actual or imputed gross income at or below 75 percent of the federal poverty guideline for one person, capped at $120 per month total split equally among that obligor's children. For parents with no gross income, who receive only means-tested assistance, or who cannot work due to a medically proven disability, incarceration or institutionalization, the presumption flips and a zero dollar order is entered.

## Can an Illinois judge depart from the guideline?

Yes, on written findings. The guideline amount is a rebuttable presumption in any judicial or administrative proceeding. The court may deviate where applying it would be inequitable, unjust or inappropriate, and any deviation has to be accompanied by written findings specifying the reasons and stating what the guideline amount would have been without the deviation.

The statute names three example reasons: extraordinary medical expenditures necessary to preserve the life or health of a party or a child, additional expenses for a child with special medical, physical or developmental needs, and any other factor the court finds appropriate after considering the child's best interests.

## How long does child support last in Illinois?

Until the child turns 18, or until 19 if the child is still attending high school. That is what the statute means by "child" in [section 505(a)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000), and it is where ordinary support ends.

College is a separate obligation with its own section.

## Do Illinois parents have to pay for college?

They can be ordered to, which puts Illinois in a small group of states. [Section 513](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000) lets the court award sums out of the property and income of either or both parties for the educational expenses of a non-minor child, as equity may require.

The limits are specific:

- **An age ceiling.** Unless the parties agree otherwise, expenses must be incurred no later than the child's 23rd birthday, and in no event later than the 25th.
- **The University of Illinois cap.** Tuition and fees may not exceed in-state tuition and fees at the University of Illinois at Urbana-Champaign for the same academic year. Housing may not exceed a double-occupancy room with a standard meal plan in a U of I residence hall.
- **What else counts.** Medical and dental expenses including insurance, reasonable living expenses during the academic year and recesses, and the cost of books and supplies.
- **When it ends.** When the child fails to maintain a cumulative C grade average without illness or other good cause, turns 23, receives a bachelor's degree, or marries. Enlisting, incarceration and pregnancy do not end it.

The court can also order both parties and the child to complete the FAFSA and other financial aid forms by their deadlines, and can require a party to fund up to five college applications, two standardized entrance exams and one exam prep course.

Two provisions to plan around. A 529 account or other college savings plan created before the dissolution is treated as a resource of the child, while a post-judgment contribution counts as coming from the party who made it. And the obligation to pay is retroactive only to the date the petition was filed, so a parent who waits three years to ask gets nothing for those three years.

## How do you change an Illinois child support order?

On a substantial change in circumstances, with one shortcut. [Section 510(a)](https://www.ilga.gov/legislation/ILCS/details?ActID=2086&ChapterID=59&ChapAct=750%2BILCS%2B5%2F&SeqStart=6200000&SeqEnd=8675000) is the general rule, and it adds that contemplation or foreseeability of a future event is neither a factor nor a defense unless the order or the parties' agreement expressly names that event.

The shortcut applies only where a party receives child support enforcement services from the Department of Healthcare and Family Services and at least 36 months have passed since the order was entered or last modified. In that case no substantial change is needed if the guideline amount is at least 20 percent different from the existing order, and no less than $10 a month different. It does not apply where the existing order came from a deviation and the circumstances behind that deviation have not changed.

One more thing that does not stop: an order for child support or maintenance is not suspended and its enforcement is not stayed while post-judgment motions or an appeal are pending. You keep paying while you argue.

Source: https://www.counselpro.ai/divorce-guide/illinois/child-support