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Illinois child support: net income, the HFS schedule, and the 146-overnight rule

Illinois runs its income shares formula on net income rather than gross. Each parent's take-home pay is figured with a standardized tax amount, the two are added, and the schedule from the Department of Healthcare and Family Services, revised on March 20, 2026, gives the amount to divide.

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At a glance

ModelIncome shares on combined monthly net income, 750 ILCS 5/505, in place since July 1, 2017
ScheduleHFS Schedule of Basic Obligations, updated every year; the 2026 version runs to $27,374.99 of combined net income a month
Shared physical care146 or more overnights a year with each parent: basic obligation x 1.5, cross-multiplied by time and offset
Minimum order$40 per child a month, $120 total, when gross income is at or below 75% of the federal poverty guideline for one person
Support endsAge 18, or 19 if still attending high school; college costs are a separate claim under 5/513
ModificationSubstantial change in circumstances, or in HFS cases a 20% gap from the guideline after 36 months
AgencyDivision of Child Support Services, Illinois Department of Healthcare and Family Services

How Illinois calculates child support

Gross income under section 505 means income from all sources, leaving out means-tested benefits such as TANF, SSI and SNAP and money received for other children in the household. Net income is gross income minus taxes. By default the taxes are a standardized tax amount: federal and state income tax for a single filer with the standard deduction, plus Social Security and Medicare. HFS publishes a gross to net conversion table that does this arithmetic for you.

A parent can use an individualized tax amount instead, based on actual withholding and filing status, but only if both parents stipulate to it or the court determines it at a hearing after financial affidavits are exchanged. The parent with the majority of parenting time is presumed to claim the children for tax purposes unless the court or the parents decide otherwise.

The court then adds both net incomes, reads the basic obligation for that combined figure and number of children from the schedule, and gives each parent a percentage share. Only the paying parent's share changes hands; the other parent's share is presumed to be spent directly on the children. Above the top of the schedule the court has discretion, but the obligation cannot be lower than the highest amount the schedule lists.

Worked example: Illinois

  1. After the standardized tax amount, Parent A takes home $5,200 a month and Parent B takes home $3,100. Combined net income is $8,300.
  2. The 2026 HFS schedule row for $8,275.00 to $8,324.99 lists $2,206 for two children.
  3. Parent A earns 62.7% of the combined net income, so Parent A's part of the obligation is $1,382; Parent B's part, $824, stays in Parent B's home.
  4. With the children living mostly with Parent B, Parent A pays $1,382 a month, or $16,584 a year, before health insurance, child care, or school and activity costs are divided.

This is an estimate, not legal advice. Figures are rounded to the dollar and leave out the insurance, childcare, and other adjustments your case may have. Try your own numbers in CoreParent's calculator, then confirm with the state's official calculator.

Shared physical care in Illinois: the 146-overnight threshold

Section 505(a)(3.8) switches to a different worksheet once each parent has the children 146 or more overnights a year, which is 40% of the year. The basic obligation is multiplied by 1.5 to reflect the cost of running two homes, each parent takes their income share of that larger figure, and each share is multiplied by the percentage of time the children spend with the other parent. The two results are offset and the parent who owes more pays the difference.

There is no gradual phase-in, so the 146th overnight matters. In the example, if Parent A has exactly 146 overnights to Parent B's 219, the shared care worksheet puts Parent A's payment at about $750 a month instead of $1,382. With exactly equal time, the difference in incomes still leaves about $419 a month flowing from Parent A to Parent B.

When there are several children and each parent has at least one of them, section 505(a)(3.9) uses split care: two worksheets, each treating the child in that home as the only child, with the smaller amount subtracted from the larger.

Health insurance and medical bills

Part of the basic obligation already covers ordinary out-of-pocket medical costs. The premium attributable to the children is added to the basic obligation and split by net income; if only the total premium is known, it is divided by the number of people covered. Coverage counts as reasonable in cost when it is no more than 5% of the providing parent's gross income, and a parent whose net income is under 133% of the federal poverty guideline cannot be ordered to pay for private coverage. Uncovered medical, dental, orthodontic and vision bills can be divided as the court orders.

Child care, school and activities

Reasonable child care that lets a parent work, train or look for work, including before and after school care and day camps when school is out, is divided by each parent's share of net income. The parent who incurs it must tell the other within 14 days of a change that would affect the yearly amount. Separately, a court may order either parent to contribute to school and extracurricular expenses that support the child's educational, athletic, social or cultural development.

Low income, imputed income and the $40 minimum

For a parent whose actual or imputed gross income is at or below 75% of the federal poverty guideline for one person, there is a presumed minimum order of $40 a month per child, with a $120 total cap split among all of that parent's children. HFS's 2026 addendum puts that line at about $998 of gross income a month. A parent with no income, only means-tested benefits, a proven disability that prevents work, or who is incarcerated is presumed to owe a zero dollar order.

If a parent is voluntarily unemployed or underemployed, support is based on potential income, weighing work history, skills, education, health, criminal records and the local job market. With too little work history to judge, potential income is presumed to be 75% of the poverty guideline. Income can only be imputed after an evidentiary hearing or by agreement, with written findings, and incarceration is never treated as voluntary unemployment.

Other children and maintenance

Support a parent actually pays under an order for a child from another relationship comes off that parent's net income. For a child supported without an order, the deduction is the lesser of what the parent actually pays or 75% of what the guidelines would require on that parent's income alone. Maintenance paid under a court order is also subtracted, and maintenance received is counted as income.

When support ends, college, and changing the order

Under section 505 a child is someone under 18, or over 18 but not yet 19 and still attending high school. College is handled separately under section 513: a court can order either or both parents to contribute to tuition, housing, books and medical costs, generally for expenses incurred before the student turns 23 and never after 25, with tuition and housing measured against the University of Illinois at Urbana-Champaign.

Section 510 allows modification on a substantial change in circumstances, and only for payments that come due after the other parent is notified of the motion. In cases where HFS provides enforcement services, an order can also be updated without a substantial change when it is at least 36 months old and differs from the guideline amount by at least 20% and $10 a month. Unpaid support accrues simple interest at the end of each month under 735 ILCS 5/12-109.

Collection and enforcement

The Division of Child Support Services at HFS opens cases, establishes and enforces orders, and processes modification requests. It reviews orders every three years, a request costs nothing, and as a rule a 20% increase or decrease is needed for a change. HFS also posts the schedule, the gross to net conversion table, the standard and shared care worksheets, and an estimator.

Documents you will need

Illinois child support FAQ

Is Illinois child support based on gross or net income?

Net. Each parent's gross income is reduced by a standardized tax amount, read from the HFS gross to net conversion table, unless the parents stipulate to or the court determines individualized taxes. The schedule is then read at combined net income.

How much is child support for 2 kids in Illinois?

At $8,300 of combined net income, the 2026 schedule lists $2,206 for two children. A parent with 62.7% of that income and fewer than 146 overnights would pay about $1,382 a month before insurance and child care.

How many overnights change child support in Illinois?

146 a year for each parent. At that point the shared physical care worksheet applies, which multiplies the basic obligation by 1.5 and credits each parent for the other's time. Below 146 there is no adjustment for parenting time in the formula.

What is the minimum child support in Illinois?

$40 a month per child, up to $120 in total, for a parent whose gross income is at or below 75% of the federal poverty guideline for one person. A parent with no income or who cannot work because of disability or incarceration is presumed to owe nothing.

Do Illinois parents have to pay for college?

A court can order it under section 513, separately from child support. Expenses generally must be incurred before the student's 23rd birthday, never after the 25th, and tuition and housing are measured against in-state costs at the University of Illinois at Urbana-Champaign.

Next steps

Sources

Verified against these official sources in October 2026:

Child support in every other state

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This is general educational information, not legal advice, and official figures change. Last verified: October 2026. Consult a licensed family-law attorney in Illinois.