IL Family LawUpdated for 2026 Guidelines

Illinois Parenting Time & Custody Overnight Calculator

Calculate custody overnights, determine annual percentage split, and verify statutory qualification for child support reductions under 750 ILCS 5/505(a)(3.8).

Direct Answer · Custody Statutory Rule (2026)

In Illinois: Parenting time directly reduces child support obligations when a non-custodial parent reaches 146 overnights per year (40% timeshare) under 750 ILCS 5/505(a)(3.8). The court calculates relief using the shared physical care shared-time formula (1.5x basic obligation). Standard rotational schedules such as 2-2-3 (182 nights) qualify for full shared-custody adjustments.

Statutory Citation: 750 ILCS 5/505(a)(3.8)Judicial Authority: Illinois Family Court GuidelinesLast Verified: October 2026

Parenting Time & Custody Overnight Calculator

Calculate annual overnights, time-sharing percentage, and state child support adjustment qualification.

Jurisdiction / State:

1. Select Parenting Schedule Pattern:

2 nights every other weekend across 26 fortnights = 52 overnights/yr (14.2%).

Summer Extra Nights:Additional summer block

Holiday Extra Nights:Thanksgiving / Winter break

Annual Time-Sharing Breakdown

Parent A (Non-Custodial)

52 nights

14.2%

Parent B (Primary)

313 nights

85.8%

Parent A: 14.2%Parent B: 85.8%

⚠️Illinois Statutory Threshold: 146 Nights (40%)

Below Threshold. Current schedule provides 52 overnights, which is 94 nights short of the 146-night threshold for Illinois. Standard sole custody support applies without automatic time-sharing discount.

Statutory Legal Reference: 750 ILCS 5/505(a)(3.8) — Shared Physical Care Shared-Time Formula (1.5x Basic Obligation). In Illinois, overnights are counted under the following rule: Under Illinois statute, each parent must exercise at least 146 overnights (40% of the year). An overnight requires the child to sleep at that parent's home.

Need Full Monthly Dollar Figures for Illinois?

Calculate net payments using Illinois's official child support schedule, health insurance add-ons, and income deductions.

Open Illinois Support Calculator →

Illinois Legal Guidelines on Custody Overnights

Statutory Threshold

146 Overnights

Equal to 40% of annual parenting time

Legal Methodology

Shared Physical Care Shared-Time Formula (1.5x Basic Obligation)

Governed by 750 ILCS 5/505(a)(3.8)

Official Overnight Counting Rule in Illinois

Under Illinois statute, each parent must exercise at least 146 overnights (40% of the year). An overnight requires the child to sleep at that parent's home.

Standard Default Possession Schedule

Alternating weekends, one weeknight dinner or overnight, alternating holidays, and 2-3 weeks in summer (~85–100 overnights).

Court Evidence & Verification Checklist for Illinois

If you are requesting or defending against a child support reduction in Illinois family court based on shared physical care, prepare the following evidence:

Keep a detailed log of exact school calendar schedules (CPS or suburban school district calendar).
Save sports team game schedules and coaching attendance sheets.
Record doctor and dental visits attended during custody periods.

Illinois Custody Overnights FAQ

What is the Illinois 146-overnight rule for child support?

Under 750 ILCS 5/505(a)(3.8), if each parent has the child for at least 146 overnights per year (40%), the court MUST use the Shared Physical Care formula. The basic support amount is multiplied by 1.5 and allocated based on percentage of overnights.

What if an Illinois parent has 145 overnights?

At 145 overnights, standard sole physical custody rules apply, and the paying parent receives no shared-time discount. Crossing into 146 overnights creates a substantial decrease in support.

Data sources & methodology

Illinois Statutory Authority750 ILCS 5/505(a)(3.8) — Official state guideline schedule and parenting time rules.
NCSL Custody GuidelinesNational Conference of State Legislatures — Shared Physical Custody and Parenting Time Models.
Illinois Family Court RulesLocal standard possession schedules, overnight definitions, and administrative calculation forms.

Methodology and citations are maintained by the ChildSupportFig editorial team. Where an official guideline schedule is not yet loaded, results are shown as model estimates and the source is stated as a reference schedule.

Not legal or financial advice. Child support is determined by a court based on your state’s official worksheet. Online estimators provide an informal planning figure only. Laws change — always confirm the current guideline with your state child support agency or a licensed family law attorney in your state before relying on any number.