Illinois child support law is changing. Senate Bill 3524 amends Sections 505 and 510 of the Illinois Marriage and Dissolution of Marriage Act, which are the provisions that govern child support calculations and child support modifications. S.B. 3524, 104th Gen. Assemb., Reg. Sess. (Ill. 2026); 750 ILCS 5/505; 750 ILCS 5/510. The Illinois General Assembly’s bill status page identifies SB 3524 as “Child Support Changes” and states that the bill passed both houses on May 21, 2026. Bill Status of S.B. 3524, 104th Gen. Assemb., Reg. Sess. (Ill. 2026). These changes are scheduled to take effect on January 1, 2027. S.B. 3524, 104th Gen. Assemb., Reg. Sess. (Ill. 2026). The new law alters how Illinois courts calculate child support in shared parenting cases, expands the concept of shared physical care, creates a new adjustment table for parents with 110 to 145 overnights, changes the minimum child support rule for low-income obligors, and creates a clearer process for child support modification when a parent is incarcerated. Id. Even before these changes, Illinois child support was based on an “Income Shares” model. The Illinois Department of Healthcare and Family Services states that Illinois replaced its former percentage-of-income model with the Income Shares Guideline Model effective July 1, 2017. Ill. Dep’t of Healthcare & Fam. Servs., Income Shares. HFS explains that Illinois child support guidelines are found in Section 505 of the Illinois Marriage and Dissolution of Marriage Act. Id.; 750 ILCS 5/505. The Income Shares model means that child support is not based solely on the paying parent’s income. Section 505 requires the Illinois court to “determine each parent’s monthly net income,” “add the parents’ monthly net incomes together,” “select the corresponding appropriate amount from the schedule of basic child support obligations,” and “calculate each parent’s percentage share of the basic child support obligation.” 750 ILCS 5/505(a)(1.5)(A)-(D). To be clear, SB 3524 does not replace the Income Shares model. SB 3524 changes how that model is applied in multiple situations. Illinois Child Support And Shared Parenting Before SB 3524 One of the most significant changes concerns shared parenting. Under the current Illinois child support framework, the shared-care calculation is tied to the number of overnights each parent exercises with the child. Before SB 3524, the shared-care benchmark was 146 overnights per year. Senator Michael Hastings’ office explained the bill lowers “the threshold for applying the shared-care formula from 146 overnights per year to 110,” […]
