What Child Support Costs for One Child in California

California child support has no fixed dollar amount — it depends on both parents' income, custody time, and other factors

California does not set a flat payment for one child. Instead, the state uses a formula that takes the combined income of both parents, how much time each parent spends with the child, and certain deductions (like taxes and health insurance costs) to calculate what the paying parent owes. Two families with one child can have very different support amounts depending on whether the parents earn $30,000 or $300,000 a year, and whether custody is split 50-50 or one parent has the child most of the time.

The formula itself is set by California Family Code Section 4055. The court or a child support agency uses it to reach a number, but that number is not final until a judge reviews it or both parents agree to it in writing. If you are trying to understand what you might owe or receive, you need to know the actual incomes involved and the custody arrangement — not just the number of children.

Key Takeaways

• California calculates child support using a formula based on both parents' gross income, the percentage of time each parent has the child, and tax deductions.
• The same child support order can range from under $200 per month to over $2,000 per month depending on the parents' earnings and custody split.
• The paying parent's income includes wages, self-employment earnings, rental income, and other sources — not just a paycheck.
• A court order or written agreement between parents is required to enforce child support; informal arrangements are not legally binding.
• The state's Department of Child Support Services can calculate and collect support if neither parent has a court order in place.

How the California formula works

The state's formula starts with gross income — all money earned before taxes, including wages, self-employment income, rental income, interest, and some benefits. It does not include welfare or SSI. Both parents' gross income is added together to get the combined parental income.

Next, the formula subtracts certain costs: state and federal taxes, Social Security taxes, health insurance premiums for the child, and mandatory union dues. What remains is the net disposable income. The formula then applies a percentage based on how much time the child spends with each parent. If one parent has the child 80 percent of the time and the other 20 percent, the percentages are different than if custody is 60-40 or 50-50.

The result is a guideline amount. If the combined income is very high (over $250,000 per year, though this threshold varies by county), the judge has discretion to order more or less than the formula suggests. If both parents agree in writing to a different amount, a judge can approve that instead of the guideline.

What income counts toward child support

California counts more than just a regular paycheck. Gross income includes W-2 wages, self-employment earnings, bonuses, commissions, rental income, interest and dividend income, pension and retirement distributions, and some types of benefits. It also includes income from a new spouse or partner if that income is used to reduce the paying parent's living expenses.

Income does not include welfare benefits (CalWORKs, TANF), Supplemental Security Income (SSI), or child support received from another child. If a parent is unemployed or underemployed, the court may impute income — meaning it assumes the parent could earn more and calculates support based on that assumed amount rather than actual earnings. This happens most often when a parent deliberately reduces income to avoid support.

Self-employed parents must provide tax returns, profit-and-loss statements, and business records to prove their income. If records are missing or unclear, the court may estimate income based on prior years or industry standards.

How custody time affects the amount

The percentage of time each parent has the child directly changes the support calculation. If one parent has the child 100 percent of the time (the other has zero), the formula produces one number. If they split time 50-50, the formula produces a different number — usually lower for the higher-earning parent, because both parents are sharing the day-to-day costs.

Custody time is measured as the number of overnights per year. A parent who has the child every other weekend plus one weeknight has roughly 35 percent of the overnights. A parent with the child Monday through Friday has roughly 71 percent. The exact percentage matters because it changes where the formula lands.

If custody changes — for example, a child moves in with the other parent — either parent can ask the court to recalculate support. The change must be significant (usually at least a 10 percent shift in overnights) for the court to modify an existing order.

Examples of what one child might cost

These examples show how the same child can have different support amounts based on income and custody. They are for illustration only and do not account for all deductions or local variations.

Scenario	Paying Parent Income	Receiving Parent Income	Custody Split	Approximate Monthly Support
Low income, unequal custody	$30,000/year	$20,000/year	80-20	$150–$300
Middle income, unequal custody	$60,000/year	$40,000/year	75-25	$400–$600
Middle income, equal custody	$70,000/year	$70,000/year	50-50	$0–$200
High income, unequal custody	$150,000/year	$50,000/year	80-20	$1,500–$2,500

These ranges reflect the formula before the court applies any adjustments. Actual orders may be higher or lower depending on special expenses (private school, medical costs), hardship deductions, or a judge's discretion at high income levels. The only way to know the exact amount for your situation is to run the numbers with actual income figures and a custody arrangement.

Where to get a calculation for your situation

If you need to know what child support would be in your case, you have several options. The California Department of Child Support Services (DCSS) has an online calculator on its website where you can enter income and custody percentages to see an estimate. This is free and does not create any legal obligation.

If you are going through a court case, your attorney or a family law mediator can run the calculation using the exact figures from your case. If you do not have an attorney, many county courts offer self-help centers that can walk you through the formula or point you to low-cost legal help.

If neither parent has a court order and you want support to be calculated and collected, you can contact your county's DCSS office to open a case. They will request income information from both parents, calculate the guideline amount, and send an order to the paying parent. If the paying parent does not respond or disagree with the amount, DCSS can ask the court to hold a hearing.

What happens after a support order is set

Once a judge signs a child support order or both parents sign an agreement, the paying parent must follow it. In most cases, the employer withholds support from the paying parent's paycheck and sends it to the state's collection system, which then pays the receiving parent. This is called wage withholding and is automatic unless both parents ask the court to waive it.

If the paying parent does not have a regular employer, they must pay directly to the state's collection system or to the receiving parent, depending on the order. Payments are due on the date specified in the order — usually the first or fifteenth of the month.

If the paying parent falls behind, the state can take action: intercepting tax refunds, placing a lien on property, suspending a driver's license, or referring the case to the district attorney for enforcement. The receiving parent can also ask the court to hold the paying parent in contempt.

Frequently Asked Questions

Does child support change if I lose my job?

Not automatically. The order stays the same until you ask the court to modify it. You must file a request showing your income has dropped and ask for a new calculation. The court will not lower support retroactively unless you filed the request before you fell behind on payments. If you stop paying without filing, you will owe back support plus interest.

What if the paying parent makes much more than the guideline cap?

California's guideline formula applies to combined parental income up to $250,000 per year (though some counties use a higher cap). Above that amount, the judge has discretion to order any amount they think is fair based on the child's needs, the parents' standard of living, and other factors. High-income cases often result in orders well above the guideline.

Can parents agree to pay less than the guideline amount?

Yes, but only if a judge approves the agreement in writing. Both parents must sign a stipulation stating they understand the guideline amount and are choosing to pay less. The judge will review it to make sure the child's needs are still met. An informal handshake deal is not enforceable.

Does child support end when the child turns 18?

In California, support usually ends when the child turns 18, unless the child is still in high school. If the child is still enrolled in high school on their eighteenth birthday, support continues until they graduate or turn 19, whichever comes first. Support also ends if the child is emancipated, joins the military, or gets married before 18.

How do I find out what the other parent's income really is?

If you are in a court case, you can request the other parent's tax returns, W-2s, pay stubs, and bank statements through the discovery process. If you are not in court, you can ask the other parent directly or contact the Department of Child Support Services, which has the power to subpoena income records. If the other parent is self-employed or has hidden income, the court can order a forensic accountant to investigate.