The Bar News

Big Change to Child Support Calculation: New Income Shares Method Takes Effect July 1

On July 1, 2017, a major change for calculating child support obligations takes effect. Last year, Public Act 99-764 was enacted. The legislation amended the Illinois Marriage and Dissolution of Marriage Act to replace the percentage guideline formula with the income shares model for calculating child support. This is a significant change that brings Illinois in line with 39 other states and the District of Columbia, which already use the income shares model.

Since 1984, Illinois has used the percentage guideline formula to determine child support. It arrives at the child support obligation by multiplying the payor's net income by a statutorily set percentage, which increases based on the number of children. This model is now considered outdated "because it does not reflect actual child rearing costs or allocate those costs between the parents." (Find out more more in the December 2016 IBJ at Rather, the old formula required payors to simply pay a percentage of their net income regardless of the actual child rearing costs. Oak Brook attorney Margaret A. Bennett believes the old model often caused acrimony between divorcing parents because it is not always perceived as equitable and accurate.

Bennett says that the perception of fairness in child support is important to getting buy-in from parents. The new income shares model is based on real data that takes factors into account other than just the income of one parent. It calculates child support using actual child-rearing costs that are based in part on data from the Bureau of Labor Statistics. The Illinois Department of Health and Family Services uses that data to publish its Schedule of Basic Child Support Obligation (the Schedule) ( The schedule was updated on April 6, 2017 to reflect a recent increase in the cost of living, Bennett says.

There's more about the new law, including a link to a gross-to-net-income conversion chart from DHS, in the June Illinois Bar Journal. Also, see Margaret Bennett's recent Family Law Section newsletter article about computing basic child support under the income shares model and an item in the June IBJ about whether the new law applies to pending cases. Finally, don't miss the ISBA's online CLE course about income shares coming up June 23.

Posted on May 30, 2017 by Mark S. Mathewson

Member Comments (1)

If you are inclined to actually read the new statute, make sure you read SB 69, recently passed by both houses and waiting the governor's signature. It makes significant changes, corrections and clarifications to the original bill, and only reading the original bill will be misleading.

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