How to calculate child support for an uncontested divorce

Last updated 2026-07-10

What is child support and who has to pay it in a divorce?

Child support is a court-ordered payment from one parent to the other, meant to cover a child's basic living costs: food, housing, clothing, education, and health care. In an uncontested divorce, both parents agree on the amount and write it into their settlement agreement. The judge still reviews it. A judge can reject a number that falls below the state guideline amount.

Every state has a mandatory child support guideline formula, required by federal law under Title IV-D of the Social Security Act ^[1]. States lose federal funding if they don't have an approved guideline. So no state lets you pick any number you want. You can agree on more than the guideline. Agreeing on less usually requires showing the court a specific reason why the lower amount still meets the child's needs.

The paying parent is usually the one with fewer overnight visits, but not always. In shared-custody arrangements where both parents have roughly equal time, the parent with the higher income may still owe support, depending on how your state's formula handles parenting time.

Which child support model does your state use?

Three main models are in use across the fifty states. Knowing which one your state uses tells you what numbers to gather before you sit down to calculate.

Model	How it works	States using it (examples)
Income Shares	Combines both parents' incomes, looks up a total support obligation on a schedule, then splits it proportionally	California, New York, Florida, Texas, Ohio, and most others (roughly 40 states)
Percentage of Income (Flat)	Applies a fixed percentage to the paying parent's income only; the other parent's income is largely ignored	Wisconsin, Nevada
Percentage of Income (Varying)	Same concept but the percentage changes based on number of children	Alaska, Arkansas, Mississippi, North Dakota, Texas (prior to 2021 reform)
Melson Formula	A more complex variant of Income Shares that first carves out a self-support reserve for each parent	Delaware, Hawaii, Montana

The federal Office of Child Support Services tracks which model each state uses and publishes state agency information ^[2]. If you're unsure, your state court's self-help center will tell you instantly.

The model matters practically. Under Percentage of Income, one number drives the result: the obligor's gross income. Under Income Shares, you need both parents' incomes, a shared-expense schedule for things like health insurance and child care, and a custody split. More inputs means more to negotiate before you sign.

For an uncontested divorce, having both figures agreed on in writing before you file makes everything faster. If you're still sorting out who earns what, now is the time to pull recent pay stubs and last year's tax returns for both of you.

What income counts in the child support formula?

This is where people get tripped up. Most states use gross income, not take-home pay, as the starting point. Gross income for child support purposes is usually broader than your W-2 box 1 figure.

Things that typically count as income: wages and salary, self-employment net profit (after legitimate business expenses), bonuses and commissions, rental income, interest and dividends, Social Security benefits (including SSDI), unemployment compensation, workers' compensation, pension and retirement distributions, and in some states, imputed income if a court believes a parent is voluntarily underemployed.

Things that typically do not count: public assistance like SNAP and Medicaid, SSI (Supplemental Security Income in most states), a new spouse's income (though a few states consider household income), and child support you receive for a child from a prior relationship.

Self-employment income deserves extra attention. Courts and state agencies add back depreciation and other non-cash deductions when calculating net profit for support purposes. If you or your spouse runs a business, the IRS Schedule C bottom line is a starting point, not the final answer ^[3].

Deductions from gross income vary by state but commonly include mandatory payroll taxes (FICA), existing court-ordered support for other children, and the cost of health insurance premiums the parent pays for the child at issue. Some states allow a deduction for prior-born children living in the home even without a court order.

How does the Income Shares model calculate child support step by step?

Income Shares is the most common model, so let's walk through it. The math looks intimidating written out. Each step is straightforward.

Step 1: Determine each parent's monthly gross income. Use the definitions above. Round to the nearest dollar.

Step 2: Add them together to get combined monthly gross income.

Step 3: Look up the basic child support obligation on your state's schedule. Every Income Shares state publishes a table: combined income on one axis, number of children on the other. The table gives you a total dollar amount.

Step 4: Calculate each parent's income share. If Parent A earns $4,000/month and Parent B earns $2,000/month, the combined income is $6,000. Parent A's share is 67%, Parent B's is 33%.

Step 5: Add work-related child care costs and the child's health insurance premium to the basic obligation. This gives you the total child support obligation.

Step 6: Multiply the total obligation by the paying parent's income share. That's the base monthly payment.

Step 7: Apply your state's parenting-time adjustment, if any. States handle this differently. Some reduce the obligation when the paying parent has more than a threshold number of overnight visits (often 92 to 110 nights per year). Others use a cross-credit formula.

Here's a rough example. Combined income of $6,000/month with one child might produce a basic obligation of $1,050 per the state schedule. Add $400 in daycare and $200 in insurance. Total obligation: $1,650. The higher earner (67% share) owes $1,105/month, reduced by whatever parenting-time credit applies.

Your state's official child support calculator runs these steps automatically once you enter the inputs. Use the official state calculator, not a generic third-party one, because the schedule underlying the math is state-specific and updated periodically.

How does parenting time affect the child support amount?

Parenting time (the number of overnights each parent has) can shift the support amount a lot, especially in Income Shares states. The logic is simple. If the paying parent has the child more nights, they're covering more direct costs themselves, so the transfer payment drops.

There is no universal threshold. California's guideline uses a continuous adjustment formula that changes with every overnight. Texas uses a flat percentage of the obligor's income and applies a reduction when the paying parent has at least 100 overnights per year ^[4]. New York's formula handles parenting time through a deviation process rather than an automatic formula.

In a truly equal-time arrangement (182 or 183 overnights each), many states still require a payment from the higher-earning parent, but the amount drops substantially compared to a sole-custody scenario. A few states, like Arizona, have a specific shared-custody formula that cross-credits each parent's obligation.

For your uncontested divorce, your custody schedule and your child support number are not separate decisions. If you're discussing 50/50 custody, run the calculator with 182 overnights for each parent. If you're discussing alternating weekends, run it with roughly 52 overnights for the visiting parent. See the difference. Then decide what you're comfortable agreeing to.

Document the agreed custody schedule clearly in your parenting plan, because the judge needs to confirm the overnights match the support calculation you've presented.

What other expenses get added on top of the base child support?

Base child support covers ordinary day-to-day costs. Courts typically add or allocate several categories of extraordinary expenses on top of it.

Health insurance premiums. If one parent carries the child on employer-sponsored insurance, most states require that cost to be factored into the support calculation, either as an add-on or as an offset.

Unreimbursed medical expenses. Many agreements split these proportionally to income, often 50/50 or by the same percentage used for the base obligation. A common threshold is $250 or $500 per year before cost-sharing kicks in.

Child care costs. Work-related daycare or after-school care is usually added to the base obligation and split proportionally. The federal child and dependent care tax credit can affect how this is calculated in some states ^[5].

Education expenses. Private school tuition, tutoring, and extracurricular activity fees get handled inconsistently. Some states add them to the formula. Others treat them as matters for the parents to negotiate.

College costs. Most state child support orders end at age 18 or high school graduation, whichever is later. A smaller group of states, including New York, New Jersey, and Massachusetts, allow courts to order contribution to college costs. If you live in one of those states, address it in your agreement now rather than litigating later.

Get these add-ons into your written settlement agreement with specific language, more than a line that says "parents will share expenses equally." Vague language causes post-divorce disputes.

Can you agree to a different amount than the state guideline says?

Yes, with limits. You can always agree to pay more than the guideline; courts approve upward deviations routinely. You can agree to less, but a judge will scrutinize it.

Federal regulations require states to include procedures for deviating from the guideline when applying it would be unjust or inappropriate ^[1]. States implement this differently. Most allow downward deviations for reasons like these: the paying parent has significantly higher costs for a child from another relationship, the child has extraordinary income of their own, the parents agreed to an offsetting property or debt arrangement, or one parent is providing unusually high in-kind support.

In practice, many family law judges are skeptical of below-guideline agreements in uncontested divorces, particularly when both parents are signing off without independent legal advice. The judge's job is to protect the child's interests, more than rubber-stamp what parents agreed to.

Say your calculated guideline amount is $1,200/month and you want to agree to $800. You need a written explanation in the agreement that justifies the difference and shows the child's needs are still being met. A vague statement that "both parties agree this is fair" is not enough in most courts.

For more on the full settlement agreement, the divorce papers article covers the document set you'll need.

How do you use your state's official child support calculator?

Every state has one. Most are free, sit on the state child support agency or court website, and require no account to use.

To find it, search "[your state] child support calculator" and look for a .gov or .state.us URL. The federal Office of Child Support Services maintains a directory of state child support agency websites ^[2] if you're having trouble.

Before you open the calculator, gather these items:

• Both parents' monthly gross income (from recent pay stubs and last year's tax returns)
• Monthly cost of health insurance the parent pays for the child
• Monthly work-related child care costs
• Your proposed custody schedule (number of overnights per year for each parent)
• Any existing court-ordered child support payments either parent makes for other children

Run the calculator with the inputs you think are correct. Then run it a second time with a different custody split to see how sensitive the number is to parenting time. That range is useful when you're negotiating.

Save or print the result. Some states let you generate a PDF from the calculator. Attach it to your settlement agreement, or at minimum reference the date and version you used. Judges and mediators appreciate documentation that shows you did this properly.

If your state's calculator is hard to use or returns an error, your county court's family law self-help center can often run it with you in person. Those centers exist specifically for self-represented filers, and they're free.

How does child support get written into an uncontested divorce agreement?

The child support order has to appear in your marital settlement agreement (sometimes called a divorce agreement, separation agreement, or stipulation), and then it gets incorporated into the final divorce decree. The decree is what the court can enforce.

At minimum, the child support section of your agreement needs to include the monthly dollar amount, who pays whom, the start date, the payment method (direct deposit, money order, or through the state's payment processing unit), how and when the amount will be reviewed for changes (usually tied to a substantial change in income or a set number of years), the allocation of health insurance and uncovered medical costs, and the allocation of child care costs.

Many states also require the paying parent's Social Security number and employer information so an income withholding order can be issued automatically. Federal law requires income withholding in all new child support orders unless both parents agree in writing to opt out ^[1].

DivorceClear's $149 document packet includes a marital settlement agreement template with the child support language courts expect. You fill in the numbers you've already calculated. This is one of those spots where a properly drafted form saves you a rejected filing.

After the judge signs the decree, register the order with your state's child support enforcement agency if your state requires it, or if you think you might need enforcement help later. Registration makes the order much easier to enforce across state lines under the Uniform Interstate Family Support Act ^[6].

What happens to child support after the divorce is final?

Child support is not permanent. It can be modified when circumstances change substantially, and it can terminate when the child reaches the age of majority.

Modification means going back to court (or using your state's administrative process) and showing a material change in circumstances: a significant income change for either parent, a change in custody arrangement, a change in the child's needs (like a new medical condition), or in some states, the passage of a set number of years. Most states define "substantial change" as a percentage difference between the current order and the recalculated guideline amount, often 10 to 20 percent ^[7].

Termination happens automatically at the age of majority in most states (18 in most, 19 in Alabama and Nebraska, 21 in some circumstances in New York). If the child is still in high school at 18, many states extend support to graduation or age 19, whichever comes first. Check your state's specific rule.

Arrearage (unpaid back support) does not go away at termination. It keeps accruing interest and can be collected indefinitely in most states through wage garnishment, tax refund intercept, license suspension, and passport denial.

Build a review clause into your agreement now. Something as simple as "either party may request a modification review if either parent's gross income changes by 15% or more" sets expectations and avoids future confusion about when going back to court makes sense.

For a broader look at total costs, the alimony article covers spousal support calculations that sometimes interact with child support.

What are the most common mistakes people make when calculating child support?

Using net instead of gross income. The formula almost always starts with gross. Running it on take-home pay understates the obligation and will get your agreement rejected or modified upward later.

Forgetting to include health insurance and child care as add-ons. These can add $300 to $800 per month to the base number in states that require them. Omit them and the agreement may look like it covers more than it does.

Using a general internet calculator instead of your state's official one. The tables underlying the formula are updated periodically. A third-party calculator may be running last year's or last decade's schedule.

Not accounting for parenting time accurately. Agreeing to 50/50 in the parenting plan but entering 80/20 in the calculator, or the reverse, creates an inconsistency the judge will notice.

Agreeing to a flat dollar amount with no adjustment mechanism. Incomes change. Children's needs change. An agreement that says "$800/month forever" with no review clause will generate a modification lawsuit within a few years.

Failing to address add-on expenses at all. "We'll figure it out" is not language a court can enforce. The agreement needs to say who pays what percentage of unreimbursed medical costs, who maintains health insurance, and how disputes about expenses get resolved.

If you're uncertain about any of these, a one-hour consultation with a divorce attorney to review your numbers usually runs $150 to $300 and is money well spent before you file.

How does child support interact with taxes?

Here the rules are simple and firm. Under federal tax law, child support payments are neither deductible by the paying parent nor taxable income to the receiving parent ^[3]. This has been true since the Tax Reform Act of 1984. Unlike alimony for pre-2019 divorces, there is no grey area.

What does affect taxes is the child dependency exemption and the child tax credit. The parent who claims the child as a dependent (usually the custodial parent by default) gets to use the child tax credit, worth up to $2,000 per child in 2024 under current law ^[5]. Parents can agree to alternate who claims the child each year. That arrangement needs to be in the written agreement, with IRS Form 8332 (Release of Claim to Exemption) signed by the custodial parent for each year they release the claim.

Some parents try to structure a lower child support amount by giving the paying parent the dependency exemption as a trade. Courts are skeptical, because it creates an annual negotiation and the tax value of the exemption fluctuates. If you do it, make the Form 8332 rotation part of the written order, not a verbal understanding.

The child and dependent care credit (for qualifying child care expenses) goes to the parent who paid the expenses. If you're splitting child care costs in the support order, clarify who claims that credit for tax purposes.

Frequently asked questions

Can we just agree on a child support amount without using the state formula?

You can agree on any amount at or above the guideline without explanation. If you want to go below the guideline, you need to document why in your agreement and a judge must approve it. Courts must find that the deviation is in the child's best interests. Most family law judges will not approve a below-guideline amount just because both parents signed off on it.

Does child support change if custody changes after the divorce?

Yes. A significant change in the custody schedule is one of the clearest grounds for a modification. If you go from alternating weekends to 50/50, either parent can file for a modification review. The new amount is calculated using the current formula and incomes at the time of the modification request, not the original divorce numbers.

What counts as gross income for child support purposes?

Gross income for child support is broader than taxable income. It typically includes wages, self-employment profit, bonuses, rental income, Social Security benefits, unemployment compensation, and workers' compensation. It generally excludes public assistance (SNAP, SSI, Medicaid) and the new spouse's income. If a court believes a parent is voluntarily underemployed, it can impute income based on earning capacity.

How is child support calculated when parents share custody 50/50?

In most Income Shares states, both parents' obligations are calculated and then cross-credited against each other. The higher earner typically still pays the difference. The exact amount depends on the income gap. In Percentage of Income states, the higher earner may owe a reduced flat percentage. Running your state's calculator with 182 overnights for each parent gives you the actual number.

Does the receiving parent have to use child support for specific things?

No. There is no requirement that the receiving parent document how child support dollars are spent. The legal theory is that the receiving parent's household costs are already supporting the child, and the payment offsets that. Courts do not audit child support spending. If you have concerns about specific expenses like extracurriculars or medical costs, address them in the written agreement as separate line items.

Can child support and property division be traded off against each other?

Property settlements and child support are legally separate. A judge reviewing a below-guideline child support agreement will not give credit for an above-average property division to the receiving parent. The child has an independent right to support that the parents cannot trade away. You can negotiate property and support simultaneously, but the support amount still has to meet the guideline independently.

What happens if the paying parent loses their job?

The obligation does not automatically suspend. The paying parent must file a modification request with the court or state agency as soon as income drops. Arrears accumulate from the current order amount until a court formally modifies it. Waiting months before filing a modification request while unemployed is one of the most common and costly mistakes in post-divorce support management.

How far back can child support be collected?

A court cannot order retroactive support before the date a case was filed in most states. Once an order exists, unpaid arrears can be collected indefinitely; there is no statute of limitations on collecting child support debt. Federal law allows collection through tax refund intercepts, wage withholding, and license suspension until the debt is paid in full.

Is child support different for self-employed parents?

Yes, the income calculation is more complex. Courts start with net self-employment income after legitimate business expenses, then add back non-cash deductions like depreciation. If a self-employed parent's reported income looks unusually low, the court may impute income based on lifestyle evidence or prior earnings history. Bring full tax returns (personal and business) to any calculation or negotiation involving a self-employed parent.

Does child support automatically end at age 18?

Not always. In most states it ends at 18 or high school graduation, whichever is later. Alabama and Nebraska extend it to 19 automatically. New York and a few other states allow courts to extend support for college or for a child with a disability well beyond the standard age. Check your state's specific statute, and address any post-18 obligations explicitly in your agreement.

Can child support be paid directly between parents, or does it have to go through the state?

Federal law requires an income withholding order in all new child support cases, meaning support is deducted from the paying parent's paycheck automatically. Parents can agree in writing to opt out of income withholding and pay directly, but many family law practitioners advise against it because direct payment creates disputes about what was paid and when. Payment through the state's processing unit generates a verifiable record.

How does a new child from a different relationship affect child support?

Having a new child does not automatically reduce support owed to children from your divorce. Most states allow a deduction from gross income for court-ordered support paid for other children, and some allow a reduction for subsequent children living in the home, but the calculation varies widely. Filing a modification request after a new child is born is the proper route; courts will weigh all children's needs.

Sources

1. U.S. Code, Title 42, Section 667 (Child Support Guidelines): Federal law requires every state to have a child support guideline formula as a condition of receiving IV-D funding, and requires income withholding in all new orders.
2. U.S. Office of Child Support Services, State Child Support Agencies Directory: The federal Office of Child Support Services tracks which income model each state uses and publishes state agency contact information.
3. IRS Publication 504, Divorced or Separated Individuals: Child support payments are neither deductible by the payer nor includible in the income of the recipient; self-employment income on Schedule C is the starting point for calculating business owner income.
4. Texas Family Code, Chapter 154 (Child Support): Texas uses a percentage-of-income model and provides a reduction in the guideline amount when the paying parent has at least 100 overnights per year.
5. IRS, Child Tax Credit and Child and Dependent Care Credit: The child tax credit is worth up to $2,000 per qualifying child in 2024; the dependency claim can be released with IRS Form 8332.
6. Uniform Law Commission, Uniform Interstate Family Support Act (UIFSA): UIFSA governs enforcement of child support orders across state lines; all 50 states have adopted it.
7. U.S. Office of Child Support Services, Essentials for Attorneys in Child Support Enforcement: Most states define a substantial change warranting modification as a 10-20 percent difference between the current order amount and the recalculated guideline amount.
8. New York State Unified Court System, Child Support (CourtHelp): New York uses an Income Shares model and allows courts to order contribution to college costs in appropriate circumstances.