The Illinois Child Support Guideline calculation allows for an adjustment in the case of shared parenting.
It also requires the designation of a majority-time parent.
In the case of equally shared parenting (50/50 time-sharing), the child support guideline calculation should not depend on which parent is designated as the majority-time parent.
The way the calculation is structured, however, it does matter.
This designation matters because the IRS ties several key tax credits (such as the dependency exemption and child tax credit) to the majority-time parent.
Depending on which parent receives those tax benefits, the guideline calculation will produce a different result. In Illinois, both results may be technically correct.
What many attorneys do is the following:
- Calculate child support with one parent designated as majority-time. (Make sure the tax designations are correct.)
- Calculate child support with the other parent designated as majority-time. (Ditto.)
- Manually take the number half-way between these two. The way to get that is to add the two numbers together and divide the result by two.
For more on the tax effects of designating one parent as the majority time parent, see this blog post.