California uses a formula based on both parents' income and custody time

California child support is calculated using a statewide formula that looks at how much each parent earns, how much time each parent spends with the child, and how many children need support. The formula is the same across all counties — a judge or child support officer plugs the numbers in and gets a result. The amount is not negotiable the way some other parts of a divorce or custody case are, though parents can agree to pay more than the formula says.

The calculation starts with gross income — that means income before taxes, not what lands in your bank account. It includes wages, self-employment income, rental income, and some benefits. Then the formula accounts for how many nights per year each parent has the child, because more parenting time means lower support.

Key Takeaways

  • California calculates child support by taking both parents' gross income, subtracting certain deductions, and running the result through a statewide formula that accounts for custody time.
  • The formula produces a guideline amount that a judge will order unless one parent shows the guideline would be unfair in that specific case.
  • Income includes wages, self-employment earnings, rental income, and some government benefits — not just a paycheck.
  • If one parent has the child more than 50 percent of the time, that parent pays less support because they are covering more of the child's living costs directly.
  • The formula changes when there are multiple children, and support ends when the child turns 18 or finishes high school, whichever is later.

What counts as income in the California formula

The formula starts with gross monthly income. This includes your salary or hourly wages, bonuses, self-employment income, rental income from property, interest and dividends, and some government benefits like unemployment insurance or disability payments. It does not include child support you are already paying for another child, spousal support you are already paying, or TANF (Temporary information for Needy Families).

If you are self-employed, you report your net self-employment income — that is, what you make after business expenses but before personal income taxes. If your income varies month to month, the court may average it over a year or use your most recent tax return. If you recently lost a job or had a major income change, you can ask the court to use a different income figure than what your tax return shows, but you have to prove the change is permanent or long-term.

Income also includes benefits like Social Security, workers' compensation, and unemployment insurance. It does not include public information like CalFresh (food stamps) or Medi-Cal, and it does not include the principal you get back when you sell an asset — only the income that asset produces.

How custody time affects the amount you pay or receive

The more time you spend with the child, the less child support you pay — or the more you receive. California counts overnights, not daytime hours. If you have the child 50 percent of the time or more, you are covering half the child's housing, food, and daily costs yourself, so the formula reduces what you owe.

The custody percentage is calculated by dividing the number of overnights you have by 365. If you have the child 182 nights per year, that is 50 percent custody. If you have 200 nights, that is about 55 percent. The court uses the custody order that is in place, or if there is no order yet, it may use the arrangement that is actually happening while the case is pending.

If one parent has the child almost all the time and the other parent has very little custody, the support amount will be higher. If custody is close to 50-50, the support amount will be lower. The formula does not eliminate support in a 50-50 custody case — it just reduces it, because one parent typically earns more than the other.

The statewide formula and how it produces a number

Once the court has gross income for both parents and the custody percentages, it runs the numbers through California's guideline formula. The formula is written in Family Code section 4055. It subtracts certain deductions from gross income — things like taxes, mandatory retirement contributions, and existing child support or spousal support obligations — to get net disposable income.

Then it applies a percentage based on how many children need support. For one child, the guideline is roughly 20 percent of the combined net disposable income. For two children, it is roughly 32 percent. For three children, roughly 40 percent. For four or more children, the percentage goes higher. The formula then allocates that total between the parents based on their income percentages and custody time.

The result is the guideline amount — what the law says child support should be. A judge will order this amount unless one parent shows that following the guideline would be unfair because of special circumstances, such as a very high income, a very low income, or unusual expenses for the child.

When a judge can order more or less than the guideline

A judge can order child support that is different from the guideline amount if the guideline would be unjust or inappropriate in that case. The law lists ten factors a judge can consider, including the child's special needs, the parents' debts, the cost of health insurance and childcare, and whether one parent is deliberately underemployed.

If one parent earns very little and the guideline amount would leave the child in poverty, a judge might order less. If one parent earns a very high income and the guideline amount seems too low to maintain the child's standard of living, a judge might order more. If the child has serious medical or educational needs, a judge might order more. If one parent is deliberately working less to avoid paying support, a judge can order support based on what that parent could earn, not what they actually earn.

To order an amount different from the guideline, the judge must write down the reasons why the guideline is unjust or inappropriate. This is called a deviation. If you think the guideline is unfair in your case, you can ask the judge to deviate, but you have to explain why and provide evidence.

Multiple children and how support changes over time

If there are multiple children, the formula calculates support for all of them together, then divides it by the number of children to get a per-child amount. If one child turns 18 and leaves home, the support amount is recalculated for the remaining children — it does not automatically drop by one-third or one-half.

Child support in California continues until the child turns 18, or until the child finishes high school, whichever is later. If the child is still in high school after turning 18, support continues through the end of that school year. Support also ends if the child gets married, joins the military, or becomes self-supporting.

If either parent's income changes significantly — a new job, a job loss, a promotion, or a major change in custody — either parent can ask the court to recalculate support. The court will not automatically recalculate; you have to file a request. A change in income of 10 percent or more is usually considered significant enough to warrant a recalculation.

How to find out what the guideline amount is for your situation

You can calculate the guideline amount yourself using California's child support calculator, which is available on the Judicial Council website. You enter both parents' gross income, the number of children, the custody percentages, and some deductions, and the calculator shows you the guideline amount.

If you are going through the court system, the child support officer or judge will do this calculation. If you and the other parent are working out an agreement without going to court, you can both use the calculator to see what the guideline says, then decide whether to agree to that amount or something different.

The calculator is a tool to understand the formula, not a legal document. The actual child support order comes from a judge or from a written agreement that you both sign and the court approves. If you are unsure how to use the calculator or what numbers to enter, a family law attorney or a local child support agency can walk you through it.

Frequently Asked Questions

Does child support change if one parent loses their job?

Not automatically. The parent who lost the job has to file a request with the court to recalculate support based on the new income. The court will not reduce support retroactively — meaning it will not go back and refund overpayments — unless the parent filed the request promptly after the job loss. If you are unemployed and cannot pay, tell the court right away rather than just stopping payments.

What if one parent is hiding income or working under the table?

The other parent can ask the court to investigate. The court can subpoena tax returns, bank records, and employer records. If the court finds that a parent is deliberately hiding income to avoid paying support, the judge can order support based on what that parent should be earning, and can also order the parent to pay the other parent's attorney fees for proving the hidden income.

Can parents agree to pay less than the guideline amount?

Yes, but the agreement has to be in writing and approved by a judge. The judge will review it to make sure it is not unfair to the child. If both parents agree and the judge approves, the amount can be less than the guideline — or more than the guideline if both parents want that.

Does child support stop if the paying parent retires?

Not automatically. Retirement income counts as income for the formula. If a parent retires and their income drops, they can ask the court to recalculate support based on retirement income. The court will consider whether the retirement was voluntary or forced, and whether the parent could have continued working.

What happens if the child spends equal time with both parents?

The formula still produces a support amount, because one parent usually earns more than the other. The higher-earning parent pays the lower-earning parent. The amount is lower than it would be in a case where one parent has most of the custody, but it is not zero.