How to Calculate Child Support in Illinois

Three Parts:Determining the Amount of Child SupportEstablishing Legal Parentage in Order to Calculate Child SupportSeeking Child Support in Illinois

In Illinois, both parents must support their child, regardless of whether they were ever married. Illinois established child support guidelines that courts must follow when calculating the amount of child support that one parent must pay to the other parent. Generally, the noncustodial parent (the parent that the child does not live with) pays support to the custodial parent (the parent that has primary custody of the child). Illinois has a variety of services available to people seeking child support, including help to establish legal parentage, and assistance in ensuring that a noncustodial parent meets his or her financial obligations to his or her children.

Part 1
Determining the Amount of Child Support

  1. Image titled Calculate Child Support in Illinois Step 1
    Determine the noncustodial parent’s gross income. To calculate the gross income of a supporting parent, you must add up the total amount of the person’s monthly income from whatever source. Sources of income can include but are not limited to:
    • Compensation for services, including fees, commissions, fringe benefits, and similar items;
    • Income derived from a business;
    • Any gains derived from property deals;
    • Interest earned;
    • Income from rents, royalties or dividends;
    • Alimony and separate maintenance payments;
    • Annuities and pensions;
    • Income from life insurance and endowment contracts;
    • Income from discharge of indebtedness;
    • Distributive share of partnership gross income;
    • Income in respect of a decedent
    • Income from an interest in an estate or trust.[1]
  2. Image titled Calculate Child Support in Illinois Step 2
    Calculate the noncustodial parent’s net income. Once you have determined the person’s gross income, you can calculate the net income by subtracting from the gross income all allowable deductions. The amount left is the net income.
    • Deduct federal and state income taxes and Social Security.
    • Deduct mandatory retirement contributions required by law or as a condition of employment (do not include voluntary contributions to a 401k or other retirement fund).
    • Deduct union dues.
    • Deduct dependent and individual health insurance premiums.
    • Deduct life insurance premiums that were court ordered to secure support payments.
    • Deduct any prior obligations of support or maintenance that are paid pursuant to court order.
    • Deduct foster care payments paid by the Department of Children and Family Services.
    • Deduct the monthly amount spent to repay certain debts, such as student loan payments or necessary medical benefits.[2]
    • To determine the amount of monthly income taxes and Social Security deductions, look at a person’s paystub to see how much is withheld on a monthly basis.
    • Even if a parent claims that he or she does not have any income, a judge may still order the person to pay child support. The judge will order child support if he or she finds that the parent could be making more money or earning an income but is failing to do so because they are not really looking for a job or they are deliberately choosing low paying positions for which they are overqualified.[3]
  3. Image titled Calculate Child Support in Illinois Step 3
    Select the appropriate percentage of net income. Under the State of Illinois’ child support guidelines, the noncustodial parent is required to pay a percentage of his or her net income in child support. The percentage a person is required to pay increases with the number of children.
    • The allowable percentage for one child is 20%.
    • The allowable percentage for two children is 28%.
    • The allowable percentage for three children is 32%.
    • The allowable percentage for four children is 40%.
    • The allowable percentage for five children is 45%.
    • The allowable percentage for six or more children is 50%.[4]
  4. Image titled Calculate Child Support in Illinois Step 4
    Calculate the amount of child support owed. You can calculate the amount of child support by first moving the decimal point two spots to the left of the percent amount (20% becomes .20) and then multiply that number by the monthly net income amount. For example, 1000 x .20 = $200 in monthly child support. This calculation of child support is used whether you are applying for long-term or temporary child support.
    • You can also calculate the percentage using a free online percentage calculator at:
    • The amount of child support will be set forth in a judge’s order (discussed in more detail below).[5]
  5. Image titled Calculate Child Support in Illinois Step 5
    Ask the court to use its discretion in calculating child support. Under Illinois law, a court may deviate from the standard child support percentage and consider other factors that may either increase or decrease a parent’s contribution to child support. In a parent’s Petition for Child Support (discussed in more detail below), a person can specifically ask the court to increase or decrease child support and set forth the reasons for this deviation from the standard percentage. In his or her Response to the Petition for Child Support, a parent can set forth his or her arguments against considering the additional expenses. If the court finds the parent’s request for additional support to be reasonable, the court may consider the following expenses in adjusting the amount of child support:
    • Health needs not covered by insurance
    • Child care
    • Education
    • Extracurricular activities[6]
  6. Image titled Calculate Child Support in Illinois Step 6
    Use an online calculator. There are online calculators that are designed to assist you in calculating the amount of child support that a noncustodial parent must pay. These calculators ask you a number of questions and then calculate the amount based on your responses. You can locate an online calculator at: You can also use the “Calculating Child Support Obligation Form” located at: Generally, you will be asked to provide the following information:
    • The number of children for whom the noncustodial parent is the legal parent and for whom you are seeking support.
    • Income of the noncustodial parent.
    • Monthly cost of family group health insurance paid by noncustodial parent.
    • Amount of monthly alimony paid by noncustodial parent to a spouse from a prior marriage.
    • Amount of monthly child support paid by noncustodial parent for children from a prior marriage
    • The county in which you live[7]

Part 2
Establishing Legal Parentage in Order to Calculate Child Support

  1. Image titled Calculate Child Support in Illinois Step 7
    Establish parentage in order to calculate child support. In order to calculate a noncustodial parent’s net income, you need access to his or her financial information. If the child’s noncustodial parent denies his parentage, you may need a legal determination of parentage in order for the noncustodial parent to be compelled by the court to turnover his financial information. If you have never been married and you are seeking child support, you should establish legal parentage of the noncustodial parent in order to have a child support determination based on the person’s financials.[8]
  2. Image titled Calculate Child Support in Illinois Step 8
    Agree voluntarily that you are a legal parent. Only legal parents are obligated to pay child support. You are a legal parent if: you are a biological parent of the child, you adopted a child, or you were married to the biological mother at the time of birth and therefore you are considered the presumed legal parent.[9] If you accept that you are the legal parent but you were not married at the time the child was born, you can voluntarily establish legal parentage.
    • To establish voluntary legal parentage, you must have the biological mother’s agreement and complete the Voluntary Acknowledgment of Paternity (VAP) form, which is located at:
    • Both the father and mother must sign the form.
    • You must then file the signed original form with Department of Healthcare and Family Services (HFS) by sending it to: Administrative Coordination Unit (ACU), 110 West Lawrence Avenue, Springfield, Illinois 62704.
    • The form can be signed either before or after the child’s birth, and is effective either when the child is born or when the document is filed with HFS, whichever is later.
    • You can not use this form if you are a same-sex couple.[10]
  3. Image titled Calculate Child Support in Illinois Step 9
    Seek legal parentage if the mother is married to someone else during the time the child was born. If the mother of your child is married or was married within 300 days of when the child was born, you can take steps to establish your legal parentage. In addition to completing and having the mother of your child sign the Voluntary Acknowledgment of Paternity (discussed above), you must also have the mother’s spouse sign a denial of parentage.
  4. Image titled Calculate Child Support in Illinois Step 10
    File a Petition to Establish Parentage. If you were never married to the other parent, you can file a Petition to Establish Parentage. You must complete the Petition and file it with your local county court clerk.
    • If you are a mother seeking to establish paternity, you can download the Petition at:
    • If you are a father seeking to establish your paternity, you can download the Petition at:
    • You must bring one original and two copies to the court clerk to be filed.
    • You must also pay a filing fee. You can contact the court to find out the amount of the fee and the accepted methods of payment for your local court.
    • You will receive a Paternity Return Date Summons document from the clerk. You must fill in your name as the petitioner and the other parent’s name as respondent, as well as the address for each person.[12]
    • Keep one copy for yourself and the other copy will be served on the respondent parent.
  5. Image titled Calculate Child Support in Illinois Step 11
    Serve the Summons and the Petition. After filing your Petition and receiving your Summons, you should take the Summons and one copy of the Petition to the local sheriff. The court clerk will be able to provide you information on where to locate the sheriff for your county.
    • The sheriff will serve (deliver a copy) to the parent for whom you are trying to establish parentage.
    • To check on the status of the service of process, you can call your local court clerk and ask when the Petition and Summons were served.
    • The document will have a return date, which is the date by which they must respond to the petition. The parent can respond by showing up in court on the return date.[13]
  6. Image titled Calculate Child Support in Illinois Step 12
    Schedule a hearing date. Once the respondent parent is served, you can contact the local court clerk to schedule a hearing date on your Petition. The clerk will provide you with a date and you must fill out and mail a copy of the Notice of Hearing to the respondent spouse.
    • Fill out the document and make two copies.
    • File the original with the court clerk and mail a copy to the respondent parent by mail. You should keep the other copy for yourself.
    • You must also fill out of a Proof of Mailing – Notice of Hearing and file the original with the court.
    • You can download a Notice of Hearing and Proof of Mailing at:
  7. Image titled Calculate Child Support in Illinois Step 13
    Attend the court hearing. Both parents are required to attend the hearing. Before court, the petitioner parent must complete and Order for Parentage & Allocation of Parental Responsibilities form by filling out both parent’s names at the top of the Order.
    • The judge may sign the order after hearing testimony.
    • If the mother denies that a petitioner father is the parent, the judge may order DNA testing. If the testing establishes parentage, a judge will issue an order establishing paternity of the father.[14]

Part 3
Seeking Child Support in Illinois

  1. Image titled Calculate Child Support in Illinois Step 14
    File an Application with Department of Healthcare and Family Services (DHS). DHS provides numerous services for people who receive public benefits and for those who do not. By completing an application for child support with DHS, you begin the process of seeking child support.
    • Depending on whether you receive benefits or not, DHS will help: search for the other parent; establish legal parentage (paternity); obtain a child support order or work to enforce an existing order; serve an “Income Withholding Notice for Child Support” on the other parent's employer; and assist in getting medical insurance for the child.
    • If the matter goes to court, DHS does not represent you in the hearing.
    • DHS only assists individuals with issues related to child support.
    • You can apply for DHS support services by calling the Child Support Customer Service Call Center at 1-800-447-4278 or by visiting a local office.
    • You can locate a local office at:
    • If you receive public benefits, you are automatically enrolled.
    • You can also apply by downloading an application form from: and mailing it to your local support center.[15]
  2. Image titled Calculate Child Support in Illinois Step 15
    Seek child support as part of your divorce. If you are planning to get divorced or are in the process of getting divorced, you can include your child support case in your divorce case.
    • If you have not yet filed for divorce, you can include in your Petition for Dissolution of Marriage, a request for child support. You can also file an Amended Petition if you failed to include a request for child support in your original Petition.
    • You can also ask for child support if you file a Petition for Legal Separation and you are the custodial parent.[16]
    • If your divorce case has been dragging on for a long time, you can file a Petition for Temporary Support and request child support if you are not already receiving it.[17]
  3. Image titled Calculate Child Support in Illinois Step 16
    File a Petition for Child Support. If you want to go to court directly and seek child support, you can file a Petition for Child Support with the clerk in the local court in the county where you reside. You can download the Petition of Child Support from: When you file the petition, you must bring one original and two copies of the form to the court clerk as well as a filing fee. You can contact the clerk and ask about the amount of the fee and the methods of accepted payment.
    • When completing the petition, you will have to provide: your name, age, address, and the county where you live; the name, age, and address of the other parent and check whether they live in Illinois; the names of the minor children for whom you are seeking support; and the percentage of income that you are requesting based on the number of children (discussed above).
    • You must also sign the petition and print or type your name.[18]
  4. Image titled Calculate Child Support in Illinois Step 17
    Serve your Petition. Once you have filed your Petition, you must serve the Petition on the other parent along with Summons that you received from the court. The Sheriff from the county where you live will be able to serve the document for you.[19]
  5. Image titled Calculate Child Support in Illinois Step 18
    Attend a hearing. Once the other parent responds to the Petition, the court will schedule a hearing to decide on the amount of child support that should be awarded. After hearing testimony and having both parents complete a Disclosure Statement regarding income assets, the judge will issue an Order that outlines the amount of monthly child support payments.[20]
  6. Image titled Calculate Child Support in Illinois Step 19
    Send a Notice to Withhold Income for Support. Once the judge issues his or her order setting forth the amount of child support, you must send a Notice to Withhold Income to the other parent’s employer. You must set forth the amounts and instructions as established by the court order.
    • The Notice directs the employer to take the child support payment out of the parent's paycheck and send it to the State Disbursement Unit (SDU).
    • The SDU send you the child support money and keeps a record of the child support payments.[21]


  • Look at your county’s website for motion and petition forms to assist you in seeking child support.
  • The judge can subpoena salary and work records if the other parent refuses to provide income information.

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Categories: Divorce | Legal Matters