Child Support in Illinois

Find out how child support is calculated in Illinois.

Both parents, whether married to one another or not, must support their children. Most states have specific rules for calculating the financial responsibilities of single, separated, or divorced parents, and for ensuring that parents pay support. Although parents can enter into agreements about child support, such agreements must, at a minimum, meet the guidelines set by law and receive court approval. This is because the right to receive support belongs to the child - not the parents.

Calculating Child Support in Illinois

Historically, Illinois courts used a "percentage based" formula for child support. However, beginning July 2017, Illinois changed its child support formula from a percentage based to an income shares model. The general idea behind the update to the child support calculation is that both parents are responsible for their share of raising their children. The "income shares model" that the state uses considers both parents' incomes, in addition to data on how much parents typically spend on children if they would have remained living together and shared finances.

Adjustments to the Formula

Judges in Illinois must begin their child support calculations by using the state's approved formula. However, courts can make adjustments if the guideline amount doesn't adequately address a child's best interests in light of all relevant factors, including:

  • the child's probable standard of living had the parents stayed together
  • the child's physical and emotional condition
  • the child's educational needs, and
  • the financial resources and needs of the child and both parents. (750 Ill. Comp. Stat. § 5/505 (2).)

In an appropriate case, a court may add expenses to the guideline amount for items, such as daycare, health care, extracurricular activities, or private school tuition. And, a very high-income parent may be able to pay more than the guideline amount, while a very low-income parent may pay less. Additionally, judges may deviate if either parent has extraordinary medical expenses, additional expenses due to the child's special needs, or for any other reason a judge believes the guidelines are inequitable, unjust, or inappropriate. (750 Ill. Comp. Stat. § 5/505 (3.4).) Judges who deviate from the guidelines must place their reasoning in writing.

Calculating Net Income for Child Support

To calculate child support in Illinois, you'll need to add up both parent's available "net income." This includes all income, whether earned or unearned, minus any applicable deductions and adjustments listed in the guidelines. Common examples of income are wages, commissions, self-employment earnings, and investment income.

Deductions include federal and state income taxes, social security tax, mandatory retirement contributions, union dues, health insurance premiums for the non-custodial parent or dependents, expenses necessary to produce income, medical expenses necessary for life or health, and any reasonable amounts already paid for the benefit of the child or the custodial parent, not including gifts.

Next, add both parent's net incomes together to find the parents' combined "adjusted net income." Using the state's "income conversion chart" (which updates each year), you will find the basic support obligation for each parent.

After determining the basic support obligation, you will need to refer to the state's "income shares schedule" to determine the amount of support for both parents. If parents are exercising shared parenting—meaning both parents have overnight parenting time with the child at least 146 times per year—after you find the basic support obligation, you must multiply it by 150% (or 1.5) to estimate the shared expenses between both parents. (750 Ill. Comp. Stat. §5/505 (1.5).)

Parents can calculate a minimum support order by using the Illinois child support calculator available from The Illinois Department of Healthcare and Family Services Division of Child Support Services (DCSS). DCSS is the state agency responsible for helping families obtain child support payment orders, locate absent parents, establish paternity if necessary, and secure compliance with child support orders. You can find more information about DCSS services for both custodial and non-custodial parents on their website.

Imputing Income for Child Support

Even if you don't have any income, you could still be responsible for child support. If a court believes a parent is voluntarily unemployed or "underemployed" (working at a lower-paying job than qualified for or working fewer hours than the parent is able to work), the judge will look carefully at the reasons for the lack of income.

Unless the parent shows evidence of serious job-hunting efforts or disability, a judge might base support on "imputed" (potential) income. Imputed income can be based on a parent's most recent job or on local job opportunities that the parent would qualify for depending on training and experience. If there is no evidence of greater earning ability, a court will probably impute income at minimum wage. (750 Ill. Comp. Stat. §5/505 (3.2).)

(To learn more about imputed income, see our article, "Imputing Income for Child Support").

Termination or Modification of Child Support in Illinois

A parent seeking modification of an existing support order must show the court there is a substantial change in circumstances since the last order, or:

  • that there is a discrepancy of at least 20% (no less than $10/month) between the existing order and a new calculation using the guidelines, or
  • demonstrate that there is a need to provide for the child's health care needs through insurance or other means. (750 Ill. Comp. Stat. §5/510.)

In Illinois, the obligation to support a child ends when the child turns 18 unless the child is still attending high school full-time, in which case it continues until the child turns 19 or graduates from high school, whichever happens first. The obligation may continue beyond this if a child is disabled and not capable of self-support. Judges in Illinois also sometimes order a non-custodial parent to help with the expenses of a child over 19 that is attending college. (750 Ill. Comp. Stat. §5/510 (g).)

If you have questions about filing for child support in Illinois, or if you would like more information on determining how much child support you'll have to pay, contact a family law attorney in your area.

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