How is child support calculated?

Child support is calculated using one of three models depending on your state: Income Shares (used by most states), Percentage of Income (used by Texas, Wisconsin, and a few others), or a Hybrid model. Each model considers the parents' incomes, number of children, and custody arrangement.

What is the Income Shares model?

The Income Shares model, used by about 40 states, calculates child support based on both parents' combined income. It estimates what the parents would have spent on the child if they were still together, then divides that amount proportionally based on each parent's share of the total income.

How Child Support Works

Q: What is imputed income?

Imputed income is income that a court assigns to a parent who is voluntarily unemployed or underemployed. If a parent deliberately works less or quits their job to reduce child support, the court can calculate support based on what they could be earning.

Understanding how courts calculate child support payments can help you determine if your current order is fair.

The Three Calculation Models

Every state uses one of three basic models to calculate child support. The model your state uses determines how income from both parents factors into the final amount.

1. Income Shares Model (Most States)

About 40 states use the Income Shares model. This approach looks at both parents' combined income and estimates what they would have spent on the child if the family were still together.

Here is how it works:

Both parents' gross incomes are added together
A state guideline table determines the total child support obligation based on combined income and number of children
Each parent's share is proportional to their percentage of the combined income
The non-custodial parent typically pays their share to the custodial parent

Example: If Parent A earns $60,000 and Parent B earns $40,000, their combined income is $100,000. Parent A earns 60% of the total, so they would be responsible for 60% of the child support obligation.

2. Percentage of Income Model

A handful of states - including Texas, Wisconsin, Mississippi, North Dakota, and Alaska - use a simpler percentage-based approach. This model only considers the non-custodial parent's income.

A flat percentage of the non-custodial parent's net (or gross) income is set as child support
The percentage increases with more children (typically 20% for one child, 25% for two, etc.)
The custodial parent's income is generally not considered

Why this matters for hidden income: In percentage states, every dollar of hidden income directly reduces child support. If your ex earns $80,000 but reports $50,000, the support could be thousands less than it should be.

3. Hybrid Model

A few states - including Delaware, Hawaii, Montana, and DC - use hybrid models that combine elements of both approaches. These may use the percentage model for lower incomes and the income shares model for higher incomes, or use other variations.

What Counts as Income

Courts define income broadly for child support purposes. It goes far beyond just a W-2 salary. Income typically includes:

Wages and salary - regular employment income
Self-employment income - profits from businesses, freelancing, gig work
Bonuses and commissions - often overlooked or underreported
Rental income - from investment properties
Investment returns - dividends, interest, capital gains
Retirement and pension payments
Trust distributions
Business perks - company car, housing allowance, expense accounts

Read our complete guide to what counts as income →

Gross Income vs. Net Income

Some states calculate support from gross income (before taxes), while others use net income (after taxes and certain deductions). Common allowed deductions include:

Federal and state income taxes
Social Security and Medicare taxes
Health insurance premiums (for the child)
Mandatory retirement contributions
Union dues
Existing child support orders for other children

What Is Imputed Income?

One of the most powerful tools courts have against income hiding is "imputed income." If a parent is voluntarily unemployed or underemployed - meaning they deliberately work less or quit their job to reduce child support - the court can calculate support based on what they could be earning.

Courts consider:

The parent's education and work history
Job opportunities in their area
Their physical and mental health
The reason for unemployment (laid off vs. quit)
Previous earning capacity

Adjustments and Deviations

Guidelines provide a starting point, but courts can deviate from the calculated amount based on factors like:

Extraordinary medical expenses for the child
Educational needs (private school, special education)
Travel costs for visitation
Shared or split custody arrangements
High income that exceeds guideline tables
Other children the parent supports

In most states, you can request a modification whenever there is a "material change in circumstances." Many states also allow automatic reviews every 3 years. A significant increase in your ex's income qualifies as a material change. Learn how to file a modification →

Cash income is harder to document but not impossible. Courts can look at lifestyle evidence, bank deposits, business records, and spending patterns. An attorney can subpoena bank records and tax returns. Learn what evidence courts accept →

In most states, a new spouse's income is not directly counted for child support calculations. However, a new spouse's income may be considered indirectly if it reduces your ex's living expenses, allowing them to contribute more to child support.

Think Your Ex Is Hiding Income?

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This information is for educational purposes only and is not legal advice. Child support laws vary by state. Consult a licensed attorney in your state for advice specific to your situation.