Illinois Child Support Estimator

Includes Shared Care (146+ Overnights) Logic (750 ILCS 5/505)

Income Mode:

Parent 1

Parent 2

Children & Expenses

Official Illinois Resources

How Illinois Calculates Support

Illinois follows an Income Shares Model under 750 ILCS 5/505. This model calculates support based on the combined net income of both parents, estimating how much would have been spent on the child if the parents lived together.

Calculation Steps:

  1. Determine Net Income: Calculate Net Income for both parents (Gross minus taxes and mandatory deductions).
  2. Combined Net Income: Add both incomes together.
  3. Basic Obligation: Find the "Basic Support Obligation" (BSO) from the Illinois Schedule based on combined income and number of children.
  4. Check for Shared Care: If both parents have at least 146 overnights, apply the Shared Care Formula (1.5x Multiplier).
  5. Prorate: Split the obligation based on each parent's percentage of the combined income.

The "Shared Physical Care" Rule (146 Nights)

One of the most critical factors in Illinois child support is the number of overnights. The formula changes drastically at 146 overnights (40% of the year).

Standard Care (< 146 Nights)

If the non-majority parent has fewer than 146 nights, they pay their full prorated share of the Basic Support Obligation.

Shared Care (146+ Nights)

If both parents have 146+ nights, the Basic Support Obligation is multiplied by 1.5. The parents then offset their obligations based on the percentage of time the child spends with the other parent. This typically results in a lower payment for the higher earner compared to the standard model.

Frequently Asked Questions

What is "Net Income" in Illinois?

Net Income is Gross Income minus Standardized Tax Amounts (Federal, State, FICA). Illinois uses a standardized table for tax conversion rather than actual tax returns. It also deducts mandatory retirement contributions and union dues.

Does remarriage affect child support?

Generally, a new spouse's income is not included in the parent's income for calculating support. However, courts may consider it if a parent claims they cannot afford support while their household expenses are being covered by a spouse.