How Child Support Calculations Use Your Income

Child support is based primarily on income, but the exact calculation depends on which state you live in and what counts as "income" under that state's rules.

Most states use one of two models: the income shares model (used by about 40 states) or the percentage of income model (used by a smaller number of states). Both start with the same question: how much money does each parent earn? But they answer it differently, and the answer changes what you owe or receive.

Income includes more than just your paycheck. It typically covers wages, salary, bonuses, commissions, self-employment income, rental income, and sometimes investment returns or retirement distributions. Some states count unemployment benefits or disability payments. Others do not. A few states have specific rules about whether overtime, tips, or seasonal work count as regular income.

The judge or child support agency in your state has a guideline that says what percentage of combined parental income goes to the child, or what percentage of one parent's income the other parent pays. That guideline is a starting point, not a final answer — judges can deviate from it if they find it unjust or inappropriate in your case, but they must document why.

Key Takeaways

• Child support calculations begin with each parent's income, which includes wages, self-employment earnings, bonuses, and sometimes rental or investment income.
• States use either the income shares model (splitting the cost of raising the child between parents based on their income proportion) or the percentage of income model (one parent pays a set percentage of their income).
• What counts as "income" varies by state — some include overtime and bonuses, others do not, and rules about unemployment or disability benefits differ.
• A judge can order child support above or below the state guideline amount if circumstances make the guideline unjust, but must explain the reason in writing.
• Income changes — job loss, a raise, or a career shift — can trigger a modification of the child support order if the change is substantial enough.

How the Income Shares Model Works

Under the income shares model, the state has a table showing what it costs to raise a child at different income levels. The table might say that raising one child costs 20 percent of combined parental income, or raising two children costs 32 percent. The exact percentage varies by state and by the number of children.

Once you know the total amount (the percentage applied to both parents' combined income), the calculation splits that amount between the parents based on what each one earns. If one parent earns 60 percent of the combined income and the other earns 40 percent, the first parent pays 60 percent of the total child support obligation and the second pays 40 percent. Usually, the parent without primary custody pays their share directly to the other parent or through the state's child support enforcement office.

This model assumes both parents contribute to the child's living expenses — one through direct payment and one through day-to-day care and housing. It also assumes the child spends time with both parents, though the amount of time can shift the calculation.

How the Percentage of Income Model Works

Under the percentage of income model, the non-custodial parent (the one who does not have primary custody) pays a flat percentage of their income to the custodial parent. The percentage varies by state and by the number of children. One state might set it at 17 percent of income for one child, 25 percent for two children, and 32 percent for three or more. Another state uses different percentages.

This model is simpler to calculate — you take the parent's income, multiply by the percentage, and that is the monthly or annual obligation. It does not directly account for the custodial parent's income, though some states allow a judge to consider it when deciding whether to deviate from the guideline.

The percentage model is less common than income shares, but it is still used in states including Texas, Florida, and a few others. It can be easier to understand and faster to calculate, but it may not account for situations where both parents have high incomes or where custody is shared equally.

What Counts as Income in Your State

The definition of income is where state rules diverge most sharply. All states count W-2 wages and salary. Most count self-employment income (though calculating it can be complex — you may need to show tax returns or business records). Many count bonuses and commissions, but some only count them if they are regular and predictable.

Overtime is a common point of disagreement. Some states include it automatically; others only count it if the parent regularly works overtime; still others exclude it entirely. Seasonal work — income that comes in bursts rather than spread across the year — is handled differently depending on the state. A few states count it as regular income; others average it over 12 months; some exclude it.

Rental income, investment returns, and retirement distributions are usually counted, but the rules vary. Unemployment benefits, workers' compensation, and disability payments are treated differently across states — some count them, others do not. If you receive income from sources beyond a regular paycheck, ask your state's child support agency or a family law attorney what your state includes.

How Custody Time Affects the Income Calculation

If both parents share custody roughly equally — say, 40 percent of the time with one parent and 60 percent with the other — many states adjust the child support calculation. The parent with less custody time may owe less, because the child spends more time in their home and they are already covering some expenses directly (food, utilities, housing).

The exact adjustment depends on the state. Some states have a formula that reduces the obligation by a percentage for each day or night the child spends with the non-custodial parent. Others require a judge to consider custody time as one factor among many. A few states do not adjust the calculation for custody time at all.

If custody changes after the order is in place — one parent moves, or the parents agree to a different schedule — that can be grounds to modify the child support order. You would need to file a motion with the court or contact your state's child support enforcement office to request a review.

When Income Changes Trigger a Modification

Child support orders are not permanent. If your income changes significantly — you lose a job, get a substantial raise, or change careers — you can ask the court to modify the order. Most states require the change to be substantial, often defined as a 10 to 15 percent increase or decrease in income, though the exact threshold varies.

A job loss does not automatically lower your obligation. You must show that the loss was involuntary and that you are making a good-faith effort to find new work. If a judge believes you quit your job to avoid child support, they may order you to pay based on your previous income anyway. Similarly, if you deliberately take a lower-paying job, a judge may "impute" income — order you to pay based on what you could earn, not what you actually earn.

To request a modification, you file a motion with the court that issued the original order, or you contact your state's child support enforcement office. The process and timeline vary by state. Some states allow modifications every few years automatically; others only allow them when circumstances change substantially.

Deviations From the State Guideline

State guidelines are starting points, not absolute rules. A judge can order child support above or below the guideline amount if the guideline would be unjust or inappropriate. Common reasons for deviation include: one parent has significantly higher income than the guideline assumes, the child has special needs or medical expenses, one parent is paying for private school, or the parents have agreed to a different amount in writing.

A judge must document in writing why they are deviating from the guideline. This written explanation becomes part of the court record and can be important if either parent later asks for a modification. If you believe the order deviates unfairly from the guideline, you can appeal it, though appeals are difficult and require showing that the judge abused their discretion.

Frequently Asked Questions

Does my ex's new spouse's income count toward child support?

No. Only the biological or adoptive parent's income counts. A stepparent's income is not included in the calculation, though a judge may consider it when deciding whether to deviate from the guideline — for example, if the stepparent's presence means the child's living expenses are lower.

What if I am self-employed or have irregular income?

Self-employment income is usually calculated by averaging your net income over the past two or three years, using tax returns as proof. If your income is highly irregular — you earn a lot some months and very little others — the court may average it, or may order you to pay a base amount plus a percentage of income above a certain threshold. Bring your tax returns and business records to court.

Can I hide income to lower my child support obligation?

Not successfully. The other parent can subpoena your tax returns, bank records, and employment records. If you are caught hiding income, a judge can order you to pay back support plus penalties, and may hold you in contempt of court. It is far better to report income changes honestly and ask for a modification if your circumstances have changed.

What happens if I lose my job?

You can ask the court to modify the order, but you must show the job loss was involuntary and that you are actively looking for new work. If you are unemployed, the court may order you to pay based on minimum wage or your previous income, depending on the state. File a modification request as soon as you lose your job — waiting months to file can result in back support owed.

Does child support change if I get a raise?

It can, but usually only if the raise is substantial — typically 10 to 15 percent or more of your income. A small raise usually does not trigger an automatic modification. The other parent would need to file a motion asking the court to review the order based on your increased income. If you voluntarily increase your income by taking a second job or overtime, a judge may or may not count that toward a modification, depending on the state.