Illinois Child Support Calculator
Illinois converts each parent's gross income to standardized net using the official HFS conversion table, combines the nets, reads the basic obligation from the income-shares schedule, and splits it by income share — with a 1.5× shared-care formula when each parent has at least 146 overnights. This calculator uses the current tables effective March 20, 2026, updated for the 2025 federal tax changes.
0–365; Parent B's overnights are inferred as 365 minus this
Estimated monthly child support
$773.28Parent A (non-majority parenting time / obligor)
Annual amount
$9,279.36Who pays
Parent A (non-majority parenting time / obligor)| Step | Amount |
|---|---|
| Parent A gross → net (non-majority parenting-time column) | $3,921.00 |
| Parent B gross → net (majority parenting-time column) | $2,468.00 |
| Combined monthly net income | $6,389.00 |
| Basic combined support obligation (1 child) | $1,260.00 |
| Parent A pro-rata share of combined net income Percent of combined net | 61.37 |
| Parent A pro-rata share of the basic obligation (obligor) | $773.28 |
| Total monthly transfer | $773.28 |
This is a guideline estimate under 750 ILCS 5/505 for informational purposes only — it is not legal advice and not a substitute for the official worksheet or a family-law attorney. Courts can deviate from guideline amounts based on statutory factors, and inputs like income determination or imputed income are ultimately decided by the court.
Illinois child support at a glance
| Model | Income shares (standardized net) |
| Tables in force | Effective Mar 20, 2026 (HFS) |
| Shared-care trigger | Both parents ≥146 overnights |
| Low-income minimum | $40/child/month (max $120) |
| Statute | 750 ILCS 5/505 |
Standardized net income
Instead of individual tax returns, Illinois uses an HFS-published conversion table that applies standardized federal/state/FICA assumptions to gross income — with separate columns for the parent with majority parenting time and the other parent (reflecting assumed filing status). The current table took effect March 20, 2026, incorporating the 2025 federal tax law changes and 2026 inflation adjustments.
Shared physical care
When each parent has the child at least 146 overnights a year (40%), 750 ILCS 5/505(a)(3.8) multiplies the basic obligation by 1.5, allocates it by income share, weights each parent's share by the other parent's percentage of time, and offsets — so the transfer shrinks as time approaches 50/50 and incomes converge.
Low-income minimums
An obligor whose gross income is at or below 75% of the federal poverty guideline (about $998/month in 2026) presumptively pays $40/month per child, capped at $120/month total — with a zero-dollar presumption for parents with no income or documented disability or incarceration.
Frequently asked questions
How does the Illinois gross-to-net conversion work?
The Department of Healthcare and Family Services publishes a standardized conversion table so both sides use the same tax assumptions: each $50 bracket of monthly gross income maps to a net figure, with one column for the parent with the majority of parenting time and another for the other parent. Parents can alternatively prove individualized net income, but the standardized table is the default. The current table is effective March 20, 2026.
What is the 146-overnight rule in Illinois?
If each parent has at least 146 overnights per year, the shared-physical-care formula applies: the schedule obligation is multiplied by 1.5, split by income share, each parent's amount is multiplied by the other parent's share of overnights, and the larger amount pays the difference. Below 146 overnights for either parent, the standard calculation applies with no automatic time credit — for example, 145 overnights gets no adjustment at all.
What did Illinois change in the 2026 tables?
HFS revised both tables effective March 20, 2026: the gross-to-net conversion now reflects the 2025 federal tax law (which made the TCJA rate structure permanent) and 2026 withholding, and the income-shares schedule's ceiling rose to $27,374.99 of combined monthly net income with inflation. The bottom tier was also realigned to the 75%-of-poverty low-income floor.
What is the minimum child support in Illinois?
For an obligor with gross income at or below 75% of the federal poverty guideline ($998/month in 2026), the presumptive order is $40 per month per child, capped at $120/month total. A zero-dollar order is presumed where the obligor has no gross income, receives only means-tested assistance, or cannot work due to documented medical disability, incarceration, or institutionalization.
How are childcare and health insurance handled?
Work-, education-, or job-search-related childcare and the child's health insurance premium are prorated between the parents by their shares of combined net income and added to the basic obligation; the parent paying the expense collects the other's share. Health coverage is presumed reasonable if it costs no more than 5% of the providing parent's gross income. Ordinary extracurriculars are already built into the schedule amounts.
Can parents deviate from the Illinois guideline?
Courts may deviate for extraordinary medical expenses, a child's special needs, or any factor making the guideline inappropriate given the child's best interests — but must state the guideline amount and reasons in writing. Support actually paid under court order for other children is deducted from a parent's net income before the calculation; without an order, the deduction is the lesser of what's actually paid or 75% of a guideline amount for that child.