Child support is based primarily on income, but the calculation varies by state and depends on what counts as income

Most states use a formula that starts with both parents' gross income — wages, salary, self-employment earnings, bonuses, and sometimes investment returns or rental income. The court applies a percentage or uses a table to determine the base support amount. However, what the law counts as "income" differs by state, and so does how much of it goes toward support. A parent earning $50,000 in one state may owe a different amount than in another.

The calculation also accounts for custody arrangements. If you have the children most of the time, the other parent typically pays you. If custody is split, both parents' incomes are considered and the higher earner usually pays the difference. Some states adjust the amount based on how many overnights each parent has.

Key Takeaways

  • Gross income — not take-home pay — is the starting point, and most states include wages, self-employment earnings, bonuses, and sometimes investment income.
  • Each state has its own income table or percentage formula, so the same income produces different support amounts in different states.
  • Custody time matters: the parent with fewer overnights usually pays, and shared custody can lower the amount owed.
  • Deductions for other children, health insurance, and childcare are common, but they reduce the amount owed rather than changing how income is counted.

What counts as income in child support calculations

States generally start with gross income — the money before taxes and deductions. This includes W-2 wages, salary, bonuses, overtime, and commissions. Self-employed parents report net business income (revenue minus legitimate business expenses). Some states also count unemployment benefits, workers' compensation, disability payments, and Social Security.

Investment income — dividends, interest, rental income — is counted in most states, though the rules vary. A few states exclude it if the amount is small. Retirement account withdrawals and lump-sum payments (like a settlement) may or may not count depending on the state and the reason for the payment. This is where the rules get specific to your location.

Income that is usually not counted includes TANF (Temporary Assistance for Needy Families), SSI (Supplemental Security Income), and need-based child support from a previous order. Some states exclude means-tested benefits entirely; others make exceptions. If you receive support for a different child, that amount is typically subtracted from your income before the calculation.

How states calculate the dollar amount owed

States use one of two main approaches: the income shares model or the percentage of income model. Most states use income shares, which combines both parents' incomes, determines a total support obligation based on a table, then divides it between parents according to their income percentage. For example, if combined income is $100,000 and the table says $1,200 per month is needed, and one parent earns 60% of the income, that parent pays $720.

A smaller number of states use a straight percentage: the paying parent owes a set percentage of gross income per child (often 17% for one child, 25% for two, 30% for three). This method is simpler but does not account for the other parent's income or how much time each parent spends with the children.

Most states also set an income cap — the calculation stops at a certain income level, often $150,000 to $250,000, though this varies. Income above the cap may still be considered, but the court has discretion about how much of it to include. This prevents extremely high earners from paying amounts that seem disconnected from the children's actual needs.

How custody time affects the amount

The parent with primary custody (more than 50% of overnights) usually receives support from the other parent. If custody is split roughly equally, both parents' incomes are still used in the calculation, but the paying parent is typically the one with higher income. The amount owed is often reduced because the lower-earning parent is already covering costs during their time.

Some states use an overnights formula: they calculate what each parent would owe if the other had full custody, then subtract the lower amount from the higher. Others adjust the percentage based on the exact number of overnights. A parent with 40% custody might pay 80% of the standard amount; a parent with 45% custody might pay 60%. The specifics depend on your state's law.

If both parents have equal custody and equal income, support may be zero or very low. Courts still have discretion to order support if one parent's income is significantly higher, because the children's standard of living may differ between households.

Deductions and adjustments that reduce the amount

After income is calculated, most states allow deductions that lower the support obligation. These typically include health insurance premiums for the children, childcare costs needed for work, and support already being paid for other children. Some states also deduct a portion of taxes owed on the income used in the calculation.

A parent with a second family or other dependents may be able to deduct support for those children, though courts are cautious about this. The logic is that you cannot pay two obligations from the same dollar. However, courts will not reduce support simply because a parent has chosen to have more children or taken on other financial obligations.

Extraordinary expenses — private school tuition, special needs care, or significant medical costs — may be split between parents on top of the base support amount. These are separate from the income calculation and are decided case by case.

What happens if income changes

Child support orders are based on income at the time the order is entered. If a parent's income rises or falls significantly — a job loss, a promotion, a business closing — the order can be modified. Most states require a change of at least 10% to 15% of the original income before a court will consider a modification, though some have no threshold.

A parent cannot simply quit a job to lower support. Courts look at whether the income loss was voluntary or involuntary. Losing a job due to layoff or business failure is treated differently than quitting to avoid support. If a parent is underemployed — working part-time when they could work full-time — the court may impute income, meaning it assigns an income level based on their earning capacity rather than what they actually earn.

To request a modification, you typically file a motion with the court that issued the original order. You will need to show current income documentation and explain the change. The process and timeline vary by state.

State-by-state variation in income rules

Because child support is set by state law, the same income produces different amounts in different states. One state might count investment income; another might not. One state might cap income at $150,000; another at $250,000. One state might use a 17% formula for one child; another might use 20%.

If parents live in different states, the state where the order was originally entered usually keeps jurisdiction, even if one parent moves. However, if both parents move to a new state, that state may take over. The Uniform Interstate Family Support Act (UIFSA) governs these situations, but the calculation rules of the relevant state still apply.

To find your state's specific rules, check your state's child support guidelines (usually available through the state court system or child support enforcement office). These documents lay out the income definition, the table or percentage, the deductions allowed, and the income cap.

Frequently Asked Questions

Does child support include my spouse's income?

No. Only the biological or adoptive parent's income is counted. A stepparent's income is generally not included in the calculation, even if they live in the household and contribute to expenses. However, a stepparent's presence may affect how much the custodial parent needs to support the children, which a court might consider in some situations.

What if I'm self-employed or have irregular income?

Self-employed income is calculated as revenue minus legitimate business expenses. If your income varies month to month, the court typically averages it over the past year or uses a recent tax return. You will need to provide business records, tax returns, and sometimes a profit-and-loss statement. If you have just started a business, the court may estimate based on industry averages or your prior employment.

Can I deduct child support I pay for another child?

Yes, in most states. If you are already paying court-ordered support for a child from a different relationship, that amount is subtracted from your income before the new support calculation. The court will want to see the existing order and proof of payment.

What if the other parent refuses to report their income?

The court can order income disclosure and may hold a parent in contempt for refusing. If a parent will not provide documentation, the judge may impute income based on tax returns, employment history, or a default amount set by state law. You can request a hearing and ask the court to compel disclosure or set income based on available evidence.

Does child support change automatically if my income changes?

No. The order stays the same until one parent files a motion to modify it. You must show a significant change in income and request the modification through the court. Some states allow modification every few years even without income change, but the burden is on you to file.