How Is Child Support Calculated: The State Guidelines, What Counts as Income, and What Can Change the Amount

Child support is calculated under the guidelines of the state handling the case, and the states do not all use the same formula. Federal law, 42 U.S.C. §667 (opens in a new tab), requires every state to have guidelines and treats the guideline amount as presumed correct, but each state picks its own model. Texas applies a percentage of the paying parent's monthly net resources, set mainly by the number of children. Illinois uses income shares, which combines both parents' net income. Delaware uses the Melson Formula. A court can depart from the guideline amount when the state's legal requirements are met, and an official calculator gives an estimate, not an order.

What decides the amount: the state's guidelines

The first question is which state's rules control the order. Federal rules set the floor for every state. Under 45 C.F.R. §302.56 (opens in a new tab), a state's guidelines must consider the parents' earnings and income, the subsistence needs of the paying parent, health care for the child, and other required factors, and the state must review its guidelines at least every four years. Within those limits, each state writes its own formula, its own income definitions and its own adjustments.

That is why a Texas percentage cannot serve as a national rule, and why an Illinois estimate tells a Texas parent very little. When parents live in different states, which state's order controls is a separate legal question from how the amount is calculated. If your case crosses state lines, the court clerk or child-support agency in the state that issued the order is the place to ask which court has authority.

A guideline calculation and a court order are also two different things. The calculation produces a presumed amount. The order, entered by a court or an authorized administrative process, is what a parent actually owes.

The three models states use

Most states fall into one of three broad models, though the details vary from state to state.

Income shares. This model estimates what the parents would have spent on the children if they lived in one household, using combined parental income and family size, and then divides that amount between the parents by income. Illinois's child-support FAQ (opens in a new tab) describes income shares as the most commonly used model. Under 750 ILCS 5/505 (opens in a new tab), Illinois finds each parent's monthly net income, adds the two together, reads the basic obligation from a schedule based on combined income and the number of children, and assigns each parent a share in proportion to income.

Percentage of income. This model applies a percentage to one parent's income, usually the parent who does not have primary custody. Texas uses a version of it based on net resources rather than gross wages.

The Melson Formula. Delaware uses this structured formula. The Delaware Family Court's formula report (opens in a new tab) treats the result as a rebuttable presumption. The formula accounts for each parent's self-support reserve, the child's primary support needs, parental income, and certain added expenses such as childcare and medical costs.

How Texas calculates child support

Texas sets its guideline in Texas Family Code §154.121 (opens in a new tab) and the percentages in Texas Family Code §154.125 (opens in a new tab). The percentage applies to the obligor's monthly net resources. The obligor is the parent ordered to pay. A separate, lower schedule applies when monthly net resources are below $1,000.

Section 154.125(a) applies the schedule to monthly net resources up to $11,700, a cap effective September 1, 2025. Texas law handles resources above that cap separately, so a parent with higher income should not assume the percentage simply continues. The Texas Attorney General's guidelines review page (opens in a new tab) explains that Texas reviews its guidelines at least every four years and lists the 2021 to 2025 and 2025 to 2029 review periods. Figures like the cap can change after a review, so check the current statute before relying on one.

The Texas Attorney General's Child Support Division (opens in a new tab) offers a calculator for estimating guideline support. The agency notes that a calculator result may differ from the amount a court sets or approves. For a fuller look at the Texas process, including collecting and ending support, see our guide to child support in Texas.

What counts as income

In Texas, the starting point is "net resources," defined in Texas Family Code Chapter 154 (opens in a new tab). Resources include wages and salary, commissions, bonuses, self-employment income, investment income, retirement benefits, Social Security benefits, certain disability benefits, unemployment benefits, workers' compensation, and other income. The law then subtracts Social Security taxes, federal income tax, state income tax, union dues, court-ordered health or dental insurance or cash medical support for the child, and certain mandatory retirement contributions. The court calculates income on an annual and average monthly basis where it can.

Texas also requires each party to provide income information, including two years of tax returns, a financial statement and current pay stubs. Gathering those records early makes any hearing or agency review easier to follow.

Illinois defines gross income broadly under 750 ILCS 5/505 (opens in a new tab) but excludes means-tested public assistance and benefits received for other children in the household. It then converts gross income to net income using statutory deductions. The statute has its own rules for self-employment income, maintenance and Social Security benefits paid for the child.

Records worth keeping, whatever the state, include:

• Current pay stubs and two years of federal tax returns.
• Records of bonuses, commissions, tips, overtime and benefits.
• Business records if you are self-employed.
• Proof of other support orders you pay.
• Health and dental insurance premium information and medical bills.
• Work-related childcare receipts.
• Parenting-time records, the existing order and any payment history.

How the number of children and other families affect the amount

In every one of these example states, more children before the court means a larger guideline amount, but the math differs. In Texas, the percentage rises with each child on the schedule above. Texas law also adjusts the calculation when the obligor has a legal duty to support children in another household, a situation often called multiple families, under provisions in Texas Family Code Chapter 154 (opens in a new tab).

Illinois reads the basic obligation from its schedule using combined net income and the number of children, then splits it between the parents. Because the two methods start from different numbers, the same family could see quite different results in Texas and Illinois.

Parenting time and shared custody

Equal or near-equal parenting time does not automatically end child support, and its effect depends on the state. In Illinois, when each parent has at least 146 overnights a year, a shared physical care formula under 750 ILCS 5/505 (opens in a new tab) applies. It multiplies the basic obligation by 1.5, divides it by income, adjusts each parent's share by the time the child spends with the other parent, and offsets the two amounts.

Delaware's formula materials (opens in a new tab) treat at least 164 overnights a year as shared equal placement and apply a parenting-time adjustment when the parent asked to pay has more than 79 but fewer than 164 overnights, subject to the formula's conditions. Texas does not use one universal shared-custody formula in Chapter 154, and equal possession does not by itself erase guideline support in Texas.

Health insurance, medical bills and childcare

These costs often sit beside the basic support amount rather than inside it.

In Texas, medical and dental support are addressed separately from basic guideline support under Texas Family Code Chapter 154 (opens in a new tab). An order can require health or dental insurance, cash medical support, and a split of reasonable and necessary uninsured medical, dental and vision costs, deductibles and copayments. These are child-support obligations and can be collected through income withholding.

In Illinois, 750 ILCS 5/505.2 (opens in a new tab) covers health insurance. Under section 505, reasonable childcare costs needed for a parent's work, schooling or job search can be divided in proportion to income, and the court can order contributions toward reasonable school and extracurricular expenses. Delaware's formula materials address work-related childcare, medical expenses, health insurance, uncovered medical costs and certain private-school expenses, and they ask parents to document childcare with records such as canceled checks, contracts and receipts.

When a parent is unemployed, self-employed or incarcerated

Changing jobs to lower income does not necessarily lower support. In Texas, when a parent is intentionally unemployed or underemployed, the court may base support on that parent's earning capacity rather than actual earnings, under Texas Family Code Chapter 154 (opens in a new tab). Texas courts may also order an unemployed or underemployed obligor to take part in employment services.

Federal rules limit how states use earning capacity. Under 45 C.F.R. §302.56 (opens in a new tab), incarceration may not be treated as voluntary unemployment when a support order is set or changed. When a state allows income to be imputed, meaning assigned based on what a parent could earn, the regulation lists factors such as assets, residence, work history, job skills, education, literacy, age, health, criminal record, job-search record, the local job market and local earnings.

Can the guideline amount be changed?

There are two different kinds of change. The first is a deviation when the order is set. Under 45 C.F.R. §302.56 (opens in a new tab), a court that departs from the guideline must make a written or on-the-record finding that the guideline amount would be unjust or inappropriate, state what the guideline amount would have been, and give reasons. Texas law lists factors a court may consider, including the child's age and needs, childcare, extraordinary education and health care costs, travel costs for possession, and debts.

The second is a modification of an existing order. Under Texas Family Code §156.401 (opens in a new tab), a Texas court may modify support when circumstances have materially and substantially changed, or when three years have passed since the order and the guideline amount would differ by at least 20% or $100. TexasLawHelp's guide to changing a child support order (opens in a new tab) lists common changes such as income, more children, insurance, living arrangements and incarceration. Illinois handles modifications under 750 ILCS 5/510 (opens in a new tab).

An order does not change on its own when income changes. Current payments generally stay due until the court or authorized review process enters a new order. Federal rules also require state agencies to offer review and adjustment, under 45 C.F.R. §303.8 (opens in a new tab), and to notify parents in covered cases of the right to request a review at least every three years, under 45 C.F.R. §308.2 (opens in a new tab).

How payments are made and enforced in Texas

Wage withholding is a common way to pay. The Texas Attorney General's wage withholding page (opens in a new tab) explains that an employer may receive an Order to Withhold Income for Child Support. Payments also go through the Texas State Disbursement Unit, which accepts methods listed on the agency's payment page (opens in a new tab), including online payment, bank drafts, cards, MoneyGram and mail. Payments can take up to seven days to post, and some methods carry convenience fees.

When support goes unpaid, the Attorney General's enforcement page (opens in a new tab) describes tools that can include income withholding, license suspension, denial of vehicle registration renewal and liens. The Child Support Division represents the State of Texas, not either parent.

Where to start

In Texas, the Attorney General's Child Support Division can help locate a parent, establish paternity, set and enforce orders, review and adjust support, and collect and distribute payments. There is no charge to apply. The agency lists a $35 annual service fee for qualifying full-service cases and a $3 monthly fee for registry-only payment processing, so confirm current fees and eligibility with the division before you apply. In Illinois, the Department of Healthcare and Family Services (opens in a new tab) offers services and an estimator.

The court clerk can explain local filing steps and accepted forms, though clerks do not give legal advice. TexasLawHelp, the Texas State Law Library and the State Bar of Texas lawyer-referral resources are other places to start. Spanish-language materials are available from TexasLawHelp en español (opens in a new tab) and the Attorney General's Spanish child-support portal (opens in a new tab), where child support appears as manutención de niños. If support is part of a divorce, our guides on how to file for divorce in Texas and how to get an uncontested divorce cover the wider process, and spousal maintenance in Texas is a separate obligation with its own rules.

Frequently asked questions about child support calculations

These answers add detail beyond the sections above.

What Spanish terms appear on Texas child support materials?

Child support is manutención de niños, and a support order is an orden de manutención de niños. Net resources appear as recursos netos or ingresos netos, income withholding as retención de ingresos, and medical support as manutención médica. The Texas Attorney General publishes Spanish child-support forms (opens in a new tab).

Is there an official Texas child support calculator?

Yes. The Texas Attorney General's Child Support Division offers a calculator for estimating guideline support. The result is an estimate, and the amount a court sets or approves may differ.

Can support for a sixth child go above 40% in Texas?

Under Texas Family Code §154.125 (opens in a new tab), support for six or more children is not less than the amount for five children. The five-child figure works as a floor rather than a fixed amount.

Does the Texas Attorney General represent me in a child support case?

No. The Child Support Division states that it represents the State of Texas. A parent who wants personal representation can hire a family law attorney or contact a legal aid office.

Finding a family law firm

If you want help with a calculation, a modification or an enforcement question, a family law attorney licensed in your state can review the order and the records behind it. You can search our directory of family law firms by city and state.