Do I Have to Pay Illinois Child Support for a Child I Just Found Out Is Mine?

 Posted on January 22, 2026 in Child Support

Finding out you are the father of a child you did not know about can turn your life upside down. You may feel shocked. You may feel ecstatic. You may even feel angry. You probably have many questions about what comes next, including whether you now have to pay child support. If you are in this situation in 2026, our DuPage County child support attorney can help you understand your rights and responsibilities.

What Does Illinois Law Say About Child Support for Newly Discovered Children?

Under Illinois law, a parent is required to give financial support to their child, but only if "paternity" has been established. Paternity means that the court acknowledges that you are the father of the child. Illinois Healthcare and Family Services explains that if needed, the alleged father of the child will be given a DNA test to establish paternity. If the court has determined that you are the father, you must pay child support, even if you did not know about the child.

Once you are legally recognized as the father, you have the same responsibilities as any other parent. This can feel unfair, especially if the other parent hid the pregnancy or did not tell you about the child for years. However, Illinois courts focus on what is best for the child, regardless of how or when you found out about it.

Can I Be Ordered to Back Pay Child Support?

In some cases, yes. If paternity is established through a court order or DNA test, the judge may order you to pay retroactive child support. This means you could be required to pay support for the time before you knew the child was yours.

Illinois law allows courts to order retroactive support all the way back to the child's birth. It is not automatic, though. The judge will look at several things, including when you found out about the child and whether the other parent tried to tell you. If the other parent purposefully hid the child from you, the judge may not order back support.

Some men are surprised to learn that they can owe thousands of dollars in retroactive support even though they have never even seen the child. This is why it is important to talk to a lawyer as soon as you find out you have a child.

How Is Child Support Calculated in Illinois?

Illinois uses a formula called the Income Shares Model under law 750 ILCS 5/505. This calculates child support based on both parents' incomes and the number of children they have to support. The court adds together the net monthly incomes of both parents and then decides what percentage of that will be paid to child support based on the number of children. 

For one child, the total monthly support obligation is around 20 percent of the combined monthly income. The court then decides how much of that each parent will pay based on their personal income and how many nights the child spends with the parent per year. The court may adjust this amount based on other factors like the cost of health insurance, daycare, or special needs the child may have.

What Should I Do If I Just Found Out I Am a Father?

If you just discovered you have a child, you should take action right away.

• Confirm paternity through a DNA test if you have any doubts that you are the child’s parent.

• Once paternity is established, work with the court to set up a child support order and parenting time schedule if you want to be involved in the child’s life.

• Do not ignore court papers or requests for paternity testing. If you do not respond, the court may enter a "default judgment" against you. This means the court makes decisions without consulting you, and there is a good chance they will favor the mother of the child. This could result in higher support payments or worse terms to the support order.

• You have the right to be involved in your child's life, so you should consider asking for parenting time or visitation rights.

• Keep records of all communication with the other parent and any payments you make. This documentation can protect you if disputes come up later.

Call a Naperville Child Support Attorney Today

Learning that you have a child you did not know about is overwhelming, but you do not have to face it alone. At Hensley Sendek Law, our DuPage County child support lawyer helps fathers understand their legal obligations and protect their rights. 

Our attorney can guide you through paternity testing, child support calculations, and the court process. Contact us at 630-358-9029 today for a free consultation about your situation.