Before and until July 1, 2017, child support obligation was calculated on the net income of the non-custodial parent. The new Income Share model however will take into account multiple factors, including both parties' income, to calculate support. There will continue to be a base obligation in addition to the prospective contribution by both parties. The base obligation will be divided by the parties' proportionate to their combined net income.
The new law gives guidance to shared parenting situations. A shared parenting situation occurs when each parent has the child for at least 146 overnights per year (40% of overnights in a year). In this situation, the base amount of total child support obligation is multiplied by 50%. This increase in allocation of child support will be applied to both parents.
Each parent's portion is cross multiplied with the percentage of time the other parent has parenting time on an overnight basis with the child. The amount of time that each parent spends with the child will factor as a percentage into the amount of child support he or she is responsible. The more time you spend with the child, the less your child support obligation will be relative to the other parent.
But, time spent with the child does not become a factor until the "146 overnights per year" threshold is met. So, under this new income share model both parents contribute to the expenses of the children in addition to the basic child support obligation.
This contribution does not include additional expenses such as child care and day care costs, extra curricular activities and medical coverage. Illinois is one of many states that will be using the Income Share model. Other states include Indiana, Iowa, Alabama, Arizona, California, Colorado, Connecticut, Florida, Idaho, Michigan, Kentucky, New York and Maine.
Total Support Obligation = (Basic obligation x % contributed to combined net income) + (Additional expenses by court x Percent contributed to combined net income)
Source: National Conference of State Legislators