Modifying Child Support After Income Increase in Illinois

23 min read
By Jonathan D. Steele
Modifying Child Support After Income Increase in Illinois

Modifying Child Support After an Income Increase in Illinois: A Comprehensive Legal Guide

Life rarely stands still after a divorce or parentage case concludes. Careers advance, businesses flourish, and income levels change—sometimes dramatically. When the parent paying child support experiences a significant income increase, the other parent often wonders: Can I modify child support to reflect this new financial reality? The answer in Illinois is yes, but the process requires understanding specific legal standards, procedural requirements, and strategic considerations.

Whether you're a custodial parent seeking an increase in support or a non-custodial parent who recently received a raise and wants to understand your obligations, this comprehensive guide will walk you through everything you need to know about modifying child support after an income increase in Illinois. We'll examine the statutory framework under the Illinois Marriage and Dissolution of Marriage Act, analyze relevant case law, and provide practical guidance for navigating the modification process in Cook County and throughout Illinois.

Understanding the Legal Framework for Child Support Modifications in Illinois

Illinois child support law is primarily governed by the Illinois Marriage and Dissolution of Marriage Act (IMDMA), codified at 750 ILCS 5/101 et seq. The specific provisions addressing child support modifications are found in Section 510 of the Act, which establishes both the grounds for modification and the procedures that must be followed.

The Statutory Basis: 750 ILCS 5/510

Section 510 of the IMDMA provides the fundamental framework for modifying child support orders. Under 750 ILCS 5/510(a)(1), a court may modify child support upon a showing of a "substantial change in circumstances." This language is deliberately broad, allowing courts to consider various changes in the parties' situations, including income increases.

Importantly, the statute also provides for an automatic basis for modification. Under 750 ILCS 5/510(a)(2), an inconsistency of at least 20% between the existing child support order and the amount that would result from application of the current guidelines constitutes a substantial change in circumstances. This provision is particularly relevant when a paying parent's income has increased significantly since the original order was entered.

The Income Shares Model in Illinois

Since July 1, 2017, Illinois has used an "income shares" model for calculating child support, replacing the previous percentage-of-income approach. Under this model, codified at 750 ILCS 5/505, courts calculate child support based on both parents' combined net incomes and the percentage of parenting time each parent exercises.

The income shares model creates a more nuanced calculation that considers:

When one parent's income increases substantially, this can shift the entire calculation, potentially resulting in a significant change to the child support obligation. Understanding this model is essential for anyone seeking to modify child support income increase Illinois cases.

What Constitutes a "Substantial Change in Circumstances"?

The phrase "substantial change in circumstances" is the cornerstone of any child support modification case. Illinois courts have developed a body of case law interpreting this standard, providing guidance on when income increases justify modification.

The 20% Variance Rule

As mentioned above, 750 ILCS 5/510(a)(2) establishes a bright-line rule: if the current guideline amount differs from the existing order by 20% or more, this automatically constitutes a substantial change in circumstances. This provision simplifies many modification cases, as parties need only demonstrate the mathematical variance rather than arguing about whether a change is "substantial."

For example, if a current child support order requires payment of $1,000 per month, and the guideline calculation based on updated incomes would produce an amount of $1,200 or more (a 20% increase), the threshold for modification is automatically met.

Case Law Interpreting Substantial Change

Illinois courts have addressed income increases in numerous appellate decisions. In In re Marriage of Putzler, 2013 IL App (2d) 120551, the court addressed how income increases should be evaluated in the modification context. The court emphasized that the focus should be on whether the change affects the child's standard of living and the parents' ability to contribute to the child's support.

In In re Marriage of Shen, 2015 IL App (1st) 130733, the First District Appellate Court (which covers Cook County) examined a case involving significant income changes and reinforced that the standard is whether the change is substantial enough to warrant court intervention. The court noted that not every income fluctuation justifies modification—the change must be meaningful and likely to continue.

Similarly, in In re Marriage of Sweet, 316 Ill. App. 3d 101 (2000), the court held that a parent's increased income, standing alone, can constitute a substantial change in circumstances warranting modification. This principle has been consistently upheld by Illinois courts.

Voluntary vs. Involuntary Income Increases

Unlike income decreases—where courts scrutinize whether the change was voluntary—income increases are generally viewed favorably by the court regardless of their source. Whether the paying parent received a promotion, changed jobs, started a successful business, or received an inheritance that generates income, the court will consider the new income level in determining whether modification is appropriate.

That said, courts do consider the nature of the income increase when evaluating permanence. A one-time bonus may be treated differently than a salary increase, and courts have discretion to consider whether income changes are likely to continue.

Who Can Request a Child Support Modification?

Under Illinois law, either parent—or the Illinois Department of Healthcare and Family Services (HFS)—can petition to modify child support. The question of who initiates the modification often depends on the nature of the income change.

Custodial Parent Seeking Increase

Most commonly, the parent receiving child support (often the custodial parent or the parent with the majority of parenting time) will seek modification when they learn that the paying parent's income has increased. This parent has a direct interest in ensuring that child support reflects the paying parent's current ability to provide for the children.

Custodial parents should be aware that they have the right to request income information from the other parent periodically. Many divorce decrees and parentage orders include provisions requiring annual exchange of financial information. If your order contains such a provision and the other parent refuses to comply, you may have grounds to compel disclosure through court action.

Paying Parent Seeking Adjustment

While less common, a paying parent who has experienced an income increase might also seek modification in certain circumstances. For example, if the parenting time allocation has shifted significantly in their favor, an income increase might actually result in a lower support obligation under the income shares formula. Additionally, a paying parent might seek to formalize an informal arrangement where they've been paying more than the court-ordered amount.

State Involvement Through HFS

The Illinois Department of Healthcare and Family Services has the authority to seek child support modifications when public assistance is involved. Under 750 ILCS 5/510.5, HFS can initiate reviews and seek modifications to ensure child support orders remain appropriate.

The Process for Modifying Child Support in Illinois

Understanding the procedural requirements for modifying child support is essential for success. The process differs slightly depending on whether you're in Cook County or another Illinois county, though the fundamental steps remain similar.

Step 1: Gathering Financial Documentation

Before filing any petition, you should gather comprehensive documentation of both parties' financial circumstances. Key documents include:

If you don't have access to the other parent's financial information, you can obtain it through discovery after filing your petition. However, having some evidence of the income increase before filing will strengthen your initial petition.

Step 2: Filing the Petition for Modification

A child support modification begins with filing a "Petition to Modify Child Support" in the court that issued the original order. In Cook County, domestic relations cases are handled by the Domestic Relations Division of the Circuit Court of Cook County. The petition must be filed in the same case number as the original divorce or parentage action.

The petition should include:

In Cook County, you may also need to complete specific local forms and comply with the Domestic Relations Division's procedures. The court maintains a self-help center at the Richard J. Daley Center for unrepresented litigants, though complex modification cases typically benefit from experienced legal representation.

Step 3: Service of Process

After filing, you must properly serve the other party with notice of the petition. Illinois Supreme Court Rules require personal service or service in accordance with court rules. In Cook County, this typically means service by a sheriff or licensed process server, though other methods may be acceptable depending on the circumstances.

Step 4: Discovery and Financial Disclosure

After the petition is served, both parties typically engage in discovery—the formal exchange of information. This may include:

Under 750 ILCS 5/505(a), courts have broad authority to order financial disclosure. Additionally, many local rules require automatic disclosure of financial information in support modification cases.

Step 5: Negotiation and Settlement Discussions

Many child support modification cases settle before trial. Once both parties' financial information is available, it's often possible to calculate the guideline support amount and reach an agreement. Settlement offers several advantages:

Any settlement must still be presented to the court for approval. Courts will review agreed modifications to ensure they serve the children's best interests.

Step 6: Court Hearing and Ruling

If the parties cannot reach agreement, the matter proceeds to a hearing before a judge. In Cook County, modifications may initially be heard by a Domestic Relations Hearing Officer before proceeding to a judge if necessary.

At the hearing, both parties will have the opportunity to present evidence, including:

The court will then apply the Illinois child support guidelines and make a determination. Under 750 ILCS 5/505, courts generally follow the guideline amount unless they find reason to deviate based on specified factors.

Calculating the New Child Support Amount

Understanding how child support is calculated under the income shares model is crucial for anyone seeking modification based on an income increase.

Determining Net Income

The first step is determining each parent's net income. Under 750 ILCS 5/505(a)(3), gross income includes:

Certain deductions are then taken to arrive at net income, including:

Applying the Guideline Table

Once both parents' net incomes are determined, they are combined, and the court applies the guideline schedule found in 750 ILCS 5/505(a)(1). This schedule, based on economic data about the cost of raising children, specifies the total support obligation based on combined net income and number of children.

For example, under the current guidelines, for one child with combined monthly net income of $10,000, the basic child support obligation is approximately $1,646 per month. If that combined income increases to $15,000 monthly, the basic obligation rises to approximately $2,155 per month.

Allocating the Obligation Between Parents

After determining the total support obligation, it is allocated between the parents in proportion to their respective net incomes. If one parent earns 70% of the combined income and the other earns 30%, the support obligation is divided accordingly.

The Parenting Time Adjustment

Illinois law includes an adjustment for shared parenting time. Under 750 ILCS 5/505(a)(3.3), when the non-residential parent has the children for at least 146 overnights per year, a shared care formula applies that reduces the support obligation. This can significantly affect the calculation when there is a near-equal parenting time split.

Additional Child-Related Expenses

Beyond the basic support obligation, courts may allocate additional expenses between the parents, including:

These expenses are typically divided in proportion to the parents' incomes, meaning an income increase may also affect the paying parent's share of these additional costs.

Practical Examples of Child Support Modification After Income Increase

To illustrate how these principles work in practice, consider the following scenarios:

Example 1: Significant Salary Increase

Michael and Jennifer divorced in 2019. At that time, Michael earned $80,000 per year and Jennifer earned $40,000 per year. They have two children who primarily reside with Jennifer. The court ordered Michael to pay $1,200 per month in child support.

In 2024, Michael received a promotion and now earns $150,000 per year. Jennifer learned about this through mutual friends and filed a petition to modify child support.

Under the income shares formula with the updated incomes (assuming Jennifer's income remained stable):

The new guideline amount of $1,672 represents a 39% increase from the original $1,200 order—well above the 20% threshold. The court would likely grant the modification.

Example 2: Business Success

David owns a small business. When his child support was established in 2020, his business was earning modest profits, and his income was determined to be $65,000 annually. The court ordered him to pay $750 per month in support for one child.

By 2024, David's business has grown substantially, and his income has increased to $200,000 per year. However, David argues that much of this income is retained in the business for growth and he doesn't personally benefit from it.

Illinois courts have consistently held that a business owner's income for child support purposes is not limited to their W-2 wages or distributions. Under 750 ILCS 5/505(a)(3), courts look at economic benefits, including retained earnings that benefit the owner. In In re Marriage of Rogers, 213 Ill. 2d 129 (2004), the Illinois Supreme Court addressed how to determine income for self-employed individuals, emphasizing that courts should consider the business owner's actual economic circumstances.

The court would likely find that David's income has substantially increased and modify support accordingly, potentially imputing income based on the business's profitability even if David chooses not to take distributions.

Example 3: Inheritance Generating Income

Sarah received an inheritance of $500,000 after her divorce. She invested this money and now earns approximately $25,000 per year in investment income. Her ex-husband, who has primary custody of their children, seeks to modify child support based on this new income.

Under Illinois law, investment income is included in gross income for child support purposes (750 ILCS 5/505(a)(3)(A)). Sarah's new investment income would be added to her other income, potentially increasing her child support obligation. While the inheritance itself is not income, the earnings it generates are.

Defenses and Arguments Against Modification

If you're the parent whose income has increased and you're facing a modification petition, you may have legitimate arguments against or limiting the modification:

Temporary or Irregular Income

If your income increase is likely temporary—such as a one-time bonus or overtime during a special project—you may argue that it doesn't represent a "substantial change" because it won't continue. Courts are generally interested in income that is predictable and ongoing.

Income Already Considered

If the income increase was anticipated and already factored into the original order, you may argue against modification. For example, if the original order included provisions for anticipated raises or promotions, the court may find that the change was already contemplated.

Changed Parenting Time

If parenting time has shifted significantly since the original order—particularly if you now have the children more often—an income increase may not result in a proportional support increase, or could even result in a decrease.

Other Changed Circumstances

Other changes may offset an income increase. For example, if you now have additional children from another relationship, if you have significant new expenses related to the children's needs, or if the other parent's income has also increased substantially, these factors may affect the calculation.

Special Considerations for High-Income Cases

Illinois law provides special rules for high-income cases. Under 750 ILCS 5/505(a)(1), the guideline schedule only provides specific figures up to a combined net income of $30,000 per month ($360,000 annually). For incomes above this threshold, courts have discretion to apply the highest guideline percentage or deviate based on the children's needs.

Case Law on High-Income Support

Illinois courts have addressed high-income support modifications in several significant cases. In In re Marriage of Turk, 2014 IL 116730, the Illinois Supreme Court considered how to calculate support when income exceeds the guideline maximum, holding that courts should consider the children's best interests and the standard of living they would have enjoyed had the family remained intact.

For parents in Chicago's financial, legal, and business communities, where high incomes are common, these cases provide important guidance. Courts will not simply cap support at the guideline maximum but will consider what level of support is appropriate given the family's circumstances.

Standard of Living Analysis

In high-income modification cases, courts often conduct a detailed analysis of the children's standard of living and needs. This may include consideration of:

Retroactivity of Modified Child Support Orders

A critical issue in modification cases is when the new support amount takes effect. Under 750 ILCS 5/510(a), modification generally cannot be made retroactive to a date before the filing of the petition for modification.

The Filing Date Rule

This means that even if you can prove the other parent's income increased years ago, you can only seek increased support from the date you file your petition forward. This rule underscores the importance of acting promptly when you learn of an income increase.

However, the modification is typically effective from the filing date, not the hearing date. So if you file your petition on January 1st and the case isn't resolved until July, the new support amount would generally be owed back to January 1st. Any difference between the old amount and the new amount during the pendency of the case becomes an arrearage (or, if support is reduced, a credit).

Strategic Timing Considerations

Given the retroactivity rules, timing your modification petition strategically is important:

Cook County-Specific Procedures and Considerations

For those in the Chicago metropolitan area, understanding Cook County's specific procedures can help navigate the modification process more effectively.

The Domestic Relations Division

Child support modifications in Cook County are handled by the Domestic Relations Division of the Circuit Court of Cook County, located at the Richard J. Daley Center in downtown Chicago. The division has specific rules and procedures that supplement the Illinois Supreme Court Rules.

Case Management and Scheduling

Cook County uses a case management system that assigns cases to specific judges and courtrooms. Modification petitions will typically be assigned to the same judge who handled the original divorce or parentage case, if that judge is still sitting. This provides continuity but may also mean dealing with a judge who is already familiar with the family's history.

Mediation and Settlement Conferences

Cook County encourages settlement of family law disputes and may require participation in mediation or settlement conferences before trial. These sessions provide opportunities to resolve modification disputes without the expense and uncertainty of litigation.

Electronic Filing Requirements

Cook County requires electronic filing (e-filing) for most documents in civil cases, including domestic relations matters. Parties must use the court's approved e-filing system, and there are specific procedures for service of process through the electronic system.

Working with Child Support Enforcement

If you're working with the Illinois Division of Child Support Services (DCSS) or have an order enforced through income withholding, there are additional considerations for modifications.

Administrative Reviews

DCSS conducts periodic reviews of child support orders and can seek modifications administratively in some cases. If you receive public assistance or have your case handled through DCSS, the agency may initiate a review on your behalf.

Updating Income Withholding Orders

After a modification is granted, if child support is collected through income withholding, the withholding order must be updated. This requires providing the new order to the paying parent's employer. The State Disbursement Unit (SDU) coordinates these payments and will need to update their records.

Tax Implications of Modified Child Support

Understanding the tax implications of child support is important when seeking or responding to a modification:

For high-income parents, working with a tax professional alongside your family law attorney can help ensure you understand the full financial implications of any modification.

Key Takeaways: Modifying Child Support After Income Increase in Illinois

To summarize the essential points for anyone seeking to modify child support income increase Illinois cases:

Frequently Asked Questions About Child Support Modification

How often can child support be modified in Illinois?

There is no specific limit on how often child support can be modified, but each modification requires showing a substantial change in circumstances since the last order. Courts will not entertain frivolous or repetitive modification requests.

Can I modify child support if my ex won't disclose their income?

Yes. If you have reasonable evidence suggesting an income increase, you can file a petition and use discovery to compel disclosure. Courts can also draw adverse inferences against parties who refuse to provide required financial information.

What if my income increased but my expenses increased too?

Increased expenses generally do not offset an income increase for child support purposes. The guidelines are based on income, not disposable income. However, certain expenses—such as supporting additional children—may be considered.

How long does a modification case take?

Simple cases that settle may resolve in 2-3 months. Contested cases requiring discovery and trial can take 6-12 months or longer, depending on court schedules and case complexity.

Do I need a lawyer for a child support modification?

While not legally required, having an experienced family law attorney significantly improves your chances of a favorable outcome, especially in complex cases involving disputed income, business ownership, or high assets.

Take Action to Protect Your Children's Financial Future

If you believe a modification of child support is warranted due to an income increase—whether you're seeking an increase or defending against one—the time to act is now. The retroactivity rules mean that every day you wait to file is a day of support you may be missing or, conversely, a day that builds potential arrearage.

Child support modifications can be complex, involving detailed financial analysis, procedural requirements, and strategic considerations. The stakes are high—these are funds that directly affect your children's quality of life, education, healthcare, and future opportunities.

At Beermann LLP, our experienced Illinois family law attorneys have extensive experience handling child support modification cases throughout Cook County and Illinois. We understand the nuances of the income shares model, the procedures in Cook County courts, and the strategies that lead to successful outcomes. Whether you're a parent seeking increased support or an obligor responding to a modification petition, we can help you navigate this process effectively.

Contact Beermann LLP today to schedule a consultation with one of our skilled family law attorneys. We'll review your situation, explain your options, and develop a strategy tailored to your circumstances. Your children deserve financial support that reflects their parents' true ability to provide—let us help you achieve that goal.

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Jonathan D. Steele

Written by Jonathan D. Steele

Chicago divorce attorney with cybersecurity certifications (Security+, CEH, ISC2). Illinois Super Lawyers Rising Star 2016-2025.

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