Do I need a lawyer to file for child support in Illinois?

No, you do not legally need a lawyer to file for Illinois child support. The Illinois Department of Healthcare and Family Services (HFS) handles administrative child-support cases free of charge for many parents. You can also file in circuit court using the Illinois Supreme Court approved forms without an attorney. Most contested cases benefit from at least an attorney consult, but representation is optional.

How is child support calculated in Illinois?

Illinois uses an income-share model under 750 ILCS 5/505. Both parents' net incomes (as calculated on the 13.3.1 financial affidavit) are combined, the support obligation is determined from a state-published table, and the obligation is allocated between the parents in proportion to their incomes. The number of overnights with each parent adjusts the calculation when one parent has 146 or more overnights per year.

What paperwork is required for an Illinois child-support case?

A petition for child support (or post-judgment modification), the Illinois 13.3.1 financial affidavit, the Illinois child-support calculation worksheet, supporting income documentation (tax returns, pay stubs, bank statements), and any existing parentage or custody orders. If you are using the HFS administrative process, the agency provides its own forms.

How long does an Illinois child-support case take?

An uncontested administrative case through HFS typically resolves in three to six months. A contested case in circuit court runs nine to eighteen months from filing to final order. Cases that involve a paternity dispute or a parent who is hard to serve can take longer.

Can I modify an existing Illinois child-support order without a lawyer?

Yes. Modification petitions follow the same process as the original case. You file a petition to modify, file an updated 13.3.1, and either reach agreement or go to a hearing. Modifications usually require a substantial change in circumstances — typically a 20 percent or more income change for either parent.

Is child support tax-deductible in Illinois?

No. Under federal tax law, child support is neither tax-deductible for the payor nor taxable income for the recipient. This has been true at the federal level since the Tax Cuts and Jobs Act took effect. Illinois state tax follows the federal treatment.

Do I Need a Lawyer for Illinois Child Support? (When You Do, When You Don't)

You are not divorcing. You are not in a custody fight. The two of you separated, the kids are settled, and you need a child-support order in place so the financial side stops being weird and awkward every month. The question on your mind is whether you really need to spend five thousand dollars on a family-law attorney to do something that, on paper, looks like a math problem.

The short answer is no, you do not always need a lawyer, and Illinois has explicitly designed several paths for parents to do this without one. The longer answer is that the path you should take depends on a few specific things about your case.

Three paths to an Illinois child-support order

Path 1: HFS administrative process (often free)

The Illinois Department of Healthcare and Family Services runs an administrative child-support program. You apply at illinois.gov/hfs/childsupport. HFS verifies income, calculates support under the statutory formula, and issues an administrative order. The agency can also enforce the order through wage garnishment and tax refund interception.

Cost: free for parents receiving public benefits. Fee-paying parents pay a $25 annual service fee. No attorney required, by design. Best fit when both parents have W-2 income, no business complications, and either agree on parenting time or already have a parenting order in place.

Drawback: the administrative process is slower than court (3-6 months typical) and the agency does not interpret unusual financial situations well. Self-employment income, deferred compensation, and stock-based compensation often trigger the agency to refer the case to circuit court.

Path 2: Circuit court, DIY

File a petition for child support in the circuit court of the county where the child lives. Use the Illinois Supreme Court approved petition forms (available at illinoiscourts.gov). You file a 13.3.1 financial affidavit alongside. The judge applies the income-share calculation.

Cost: $250 to $337 filing fee plus your time. Fee waiver available for low-income filers. No attorney required.

Best fit when: you and the other parent generally agree on the support number, you can both fill out the paperwork, and you just need a judge to enter the order. Many Illinois counties offer self-help centers at the courthouse to walk pro se parents through the forms.

Path 3: Circuit court with an attorney

File the same petition, but with a family-law attorney representing you. Cost: $1,500 to $5,000 for a simple uncontested case, $5,000 to $20,000+ for a contested case.

Best fit when: you and the other parent disagree about the income number, one of you is self-employed with complicated income, paternity is disputed, the other parent is hard to find or won't engage with the process, or one of you is asking for support that deviates from the statutory formula.

How Illinois actually calculates child support

Illinois switched from the old "percentage of obligor income" model to an income-share model in 2017. The formula, in plain English:

Each parent's net monthly income is calculated from line 7 of their 13.3.1.
The two net incomes are combined into the parents' combined net income.
The combined net income is looked up on the Illinois income shares schedule, which yields the basic monthly support obligation for the number of children involved.
The basic obligation is allocated between the parents in proportion to their incomes. If you earn 60 percent of the combined income, you owe 60 percent of the obligation.
If a parent has 146 or more overnights per year with the children, the calculation switches to the "shared physical care" formula, which adjusts the obligation downward.

The income shares schedule is published by the Illinois Department of Healthcare and Family Services. You can look up your number on their online calculator.

Why the 13.3.1 is the foundation

Every step of the Illinois child-support calculation starts with line 7 (net monthly income) of the financial affidavit. If your 13.3.1 is wrong, the support order is wrong. If you understate your income, you may face a contempt finding later. If you overstate it, you pay more than the formula requires.

This is why even DIY filers should take the 13.3.1 seriously. The form is not just a disclosure. It is the input to the formula that determines what hits your bank account every month for the next decade.

The 13.3.1 line-by-line guide walks every line. The DIY guide covers the documents and the four mistakes to avoid.

When you should not DIY

Be honest with yourself. Get an attorney if any of these apply:

One of you is self-employed with income that varies materially year to year. The court can impute income (assign you a higher number than your tax return shows), and you want a lawyer in the room when that happens.
Paternity is disputed. Establishing paternity is its own legal process with its own forms.
One parent has stock-based compensation or deferred comp. The classification of unvested RSUs and stock options as income or asset is non-obvious.
One parent lives out of state. Interstate child-support enforcement (UIFSA) adds a procedural layer.
The other parent is fighting it. If you cannot agree on the income number, you need representation.

Hybrid: DIY the paperwork, hire for review

The cheapest realistic path for most parents is:

Draft your own 13.3.1 (or use a tool like Casefile to assemble it).
Pay an Illinois family-law attorney for a one-hour review consult — $250 to $600 in 2026.
Either file pro se or, if the consult reveals complications, hire the attorney for the full case.

This hybrid path catches the line-classification mistakes that DIY filers make most often, without paying for full representation when the case is straightforward. Most Illinois family-law attorneys offer review-only or limited-scope engagements explicitly for this use case.

Modifications down the road

Roughly 35 percent of Illinois child-support orders get modified within five years of the original entry. The most common triggers: one parent's income changes by 20 percent or more, the parenting schedule changes substantially, or a child ages out and the basic obligation needs to be recalculated.

Modifications follow the same process as the original case. You file a petition to modify, file an updated 13.3.1, and either reach agreement or go to a hearing. If you used Casefile for the original 13.3.1, your account still has your source documents — running an updated 13.3.1 for the modification typically takes thirty minutes.

The bottom line

You do not need a lawyer to get an Illinois child-support order in the simple case. You do need a clean, accurate 13.3.1 — whether you draft it yourself, use software, or pay an attorney to draft it.

If your case is uncomplicated, HFS administrative or circuit court pro se are both real options. If your case has any of the complications above, a review consult or full representation pays for itself.

For everyone, the foundation is the financial affidavit. Get that right and everything downstream is easier. Get that wrong and everything downstream is broken.

Read the founder story if you want to know why this product exists. Read the cost guide for the full picture if your child-support case is part of a divorce. And see the attorney paperwork fees guide if you want a transparent read on what attorneys actually charge.

Do I need a lawyer for Illinois child support?