Paternity Law Basics in Illinois
Posted on February 19, 2026 in Paternity
When a child is born to married parents, the husband is assumed to be the father. When a child is born to unmarried parents in Illinois, "paternity" must be established. Establishing legal paternity is an important step that affects the child and both parents.
If you are dealing with paternity questions in Illinois in 2026, understanding how Illinois paternity law works can help. A Wheaton paternity lawyer can guide you through the process.
What Is Paternity and Why Does It Matter?
Paternity is the legal recognition of who a child's father is. Establishing paternity creates legal rights and responsibilities for the father and the child. The father gets the right to seek custody and parenting time (if the parents live separately), make decisions about the child's education and healthcare, and have a legally-acknowledged relationship with his child. The child gains the right to financial support, inheritance, and benefits like Social Security or health insurance.
Without established paternity, an unmarried father has no legal right to his child, even if he has been involved since birth. A mother cannot get child financial support from an unmarried father until paternity is established.
How Do You Establish Paternity in Illinois?
Illinois law has a few ways to establish paternity:
Voluntary Acknowledgment of Paternity
The simplest way to establish paternity is through a Voluntary Acknowledgment of Paternity form. Under 750 ILCS 46/301, both parents can sign this form at the hospital when the child is born. They can also sign it later at a local health department or vital records office. Once signed and filed, this document has the same legal effect as a court order.
This is a serious legal document. Once filed, it can only be challenged within 60 days or if there was a substantial error (like the mother lying about who the father was).
Genetic Testing
If there is disagreement about who the father is, either parent can request genetic testing through the court. These tests are more than 99 percent accurate.
Court Order
When paternity is disputed or when one parent will not cooperate, you can file a petition with the court to establish paternity. The court will review evidence, order genetic testing if needed, and then issue an order determining who the legal father is.
What Rights Does a Father Have After Paternity Is Established?
Once paternity is established, fathers have the same legal rights as fathers in marriages. These rights are protected by Illinois law.
Fathers can legally:
- Seek "allocation of parental responsibilities," which includes decision-making authority about education, healthcare, religion, and extracurricular activities
- Request parenting time
- Access school and medical records
- Object to adoption proceedings
- Participate in court cases involving the child
Establishing paternity does not automatically give a father custody or parenting time. These are separate processes in court, and the father must file separate petitions for them.
What Responsibilities Come With Paternity in Illinois?
The most significant responsibility is child support. Fathers legally must contribute money based on their income and Illinois' child support guidelines. Child support usually covers living expenses like food, clothing, and housing. It may also include medical expenses, daycare costs, and educational expenses.
Fathers are also responsible for providing health insurance for the child if it is available through their employer at a reasonable cost. This responsibility continues until the child turns 18 or graduates from high school, whichever comes later.
Can Paternity Be Challenged After It Is Established?
Illinois law makes the process of challenging paternity difficult because the courts focus on stability for children, but paternity can be challenged. Courts are cautious about disestablishing paternity when a father has acted as the child's parent for years, even if genetic testing later shows he is not the biological father.
If you are within the 60-day window from filing, you can file a rescission. You may be able to challenge paternity after the 60-day window if you can prove "fraud," "duress," or a "material mistake of fact." This requires clear and convincing evidence that you are not the biological father and that you did not know at the time of establishing paternity. It must also usually be done within two years of establishing paternity.
Call a DuPage County, IL Paternity Lawyer Today
Whether you need to establish paternity, seek child support, or challenge paternity based on new information, we can help.
Our Wheaton paternity attorneys at Andrew Cores Family Law Group offer free consultations to help you understand what your options are. Attorney Cores is currently a Fellow for the Collaborative Law Institute of Illinois and also served as a past member of his TEC Committee. Contact us at 630-871-1002 today to discuss your case.
