Child support laws in Illinois differ from those in other states. Most states use one of three child support guideline models: the income shares model, the percentage of income model or the Melson formula. Illinois uses the percentage of income model, according to the National Conference of State Legislatures.
In the income shares model, the child receives the same proportion of parental income that would have been received if the parents were still together. In the percentage of income model, the child receives a percentage of the noncustodial parent's income. The Melson formula uses public policy judgments to ensure that the parents' needs are met, as well as the child's.