California uses a formula based on both parents' income and custody time
California child support is calculated using a statewide formula set by law, not by a judge's discretion or what either parent thinks is fair. The formula takes the parents' combined gross income, subtracts certain deductions, and then splits the support obligation based on how much time each parent spends with the child and how much each parent earns. The result is a monthly payment amount that one parent owes the other.
The formula applies in almost all cases — whether parents are married, divorced, never married, or separating. The only time a judge can order a different amount is if both parents agree in writing or if following the formula would be unjust under specific circumstances defined by California law.
Understanding how the calculation works matters because you can predict roughly what the amount will be before you walk into court, and you can spot errors if a calculation seems wrong.
Key Takeaways
- California's formula multiplies each parent's net income by a percentage that depends on custody time, then subtracts tax credits and existing support obligations.
- Gross income includes wages, self-employment income, rental income, and some benefits, but excludes means-tested welfare and certain other sources.
- The percentage each parent pays rises if they have the child less than half the time, because the other parent bears more daily costs.
- The court order includes a base amount plus adjustments for health insurance, childcare, and extraordinary expenses like private school.
- Either parent can request a recalculation if income changes by 10 percent or more, or three years pass since the last order.
What counts as income in the California formula
The formula starts with gross income, which is broader than just a paycheck. Gross income includes wages and salary, self-employment net income, rental and investment income, interest and dividends, social security benefits (except SSI), unemployment insurance, workers' compensation, disability insurance, and spousal support received from anyone. It also includes income from trusts, annuities, and pensions.
Income that does not count includes Supplemental Security Income (SSI), CalWORKs (California's welfare program), food stamps, and housing assistance. Foster care payments and adoption assistance do not count either. If a parent is voluntarily unemployed or underemployed — meaning they could earn more but choose not to — the court may assign them "imputed income" based on what they could reasonably earn, though this requires a hearing and proof.
Self-employed parents must provide tax returns and business records. The court looks at net self-employment income (revenue minus legitimate business expenses) averaged over the most recent two to three years to smooth out year-to-year swings.
How custody time affects the payment amount
The percentage each parent pays depends on how many overnights the child spends with each parent per year. If one parent has the child 50 percent of the time, the payment obligation is split differently than if one parent has the child 20 percent of the time. The parent with fewer overnights typically pays more because the other parent covers more of the daily living costs — food, utilities, rent.
California counts overnights, not daytime hours. An overnight is any night the child sleeps at a parent's home. If parents share custody equally (roughly 182 overnights each per year), the formula still applies, but the payment may be lower or even zero depending on the income difference. If one parent has the child 80 percent of the time and the other 20 percent, the parent with 20 percent pays a higher percentage of their income.
The court uses the custody order in place at the time of the child support order. If custody changes later, either parent can ask the court to recalculate support based on the new arrangement.
The step-by-step calculation process
The formula works in this order:
- Add both parents' gross income together to get combined income.
- Subtract mandatory deductions: state and federal income tax, Social Security tax, health insurance premiums, and union dues.
- Subtract the cost of childcare required so a parent can work.
- Subtract existing child support or spousal support the parent pays to others.
- Multiply the result by a percentage based on custody time — typically 17 to 25 percent of net income, depending on how many overnights each parent has.
- Divide the total support obligation between the two parents based on their income ratio.
- The parent with the lower custody percentage pays their share to the other parent.
- Add adjustments for health insurance premiums, childcare costs, and extraordinary expenses.
The court order will show the base support amount plus line items for these add-ons. If health insurance for the child costs $200 per month and the non-custodial parent pays 60 percent of support, they pay $120 of that insurance cost on top of the base amount.
Income limits and the maximum support amount
California law sets a cap on the income used in the formula. As of 2024, the cap is $250,000 per month in combined parental income, though this amount adjusts annually. If both parents' combined income exceeds the cap, the court can still order support above the formula amount, but it must state its reasons in writing.
There is no minimum support amount. If both parents earn very little or have equal custody and similar income, the support obligation can be zero or close to it. However, if one parent earns significantly more, they will owe support even if the other parent also works.
The cap exists because the formula was designed for typical family incomes, and judges need flexibility when dealing with very high earners. A parent earning $500,000 per year would not pay support calculated on that full amount; instead, the court uses the capped amount and may add a discretionary amount based on the child's actual needs and the parents' standard of living.
Adjustments for health insurance, childcare, and special expenses
The base formula amount is not the final number. The court adds separate line items for costs that vary by family. Health insurance premiums for the child are divided between parents based on their income ratio. If the non-custodial parent's employer offers health insurance for the child at $150 per month, and that parent earns 60 percent of the combined income, they pay $90 of that premium as an add-on to base support.
Childcare costs required for a parent to work are also divided. If the custodial parent pays $1,200 per month for daycare so they can work, and the non-custodial parent earns 65 percent of combined income, they pay $780 of that cost. This is subtracted from their income before the formula is applied, which lowers the base amount, then added back as a separate line item.
Extraordinary expenses — private school tuition, special education, orthodontia, sports or music lessons — can be added if the court finds them reasonable and necessary. These are typically split based on income ratio, not included in the base formula.
When and how to request a recalculation
Either parent can ask the court to recalculate support if circumstances change. The most common triggers are a job loss, a significant raise, a change in custody time, or the passage of time. California law allows a recalculation if income has changed by 10 percent or more since the last order, or if three years have passed since the order was made.
To request a recalculation, file a motion with the court that issued the original order. You will need to provide current pay stubs, tax returns, and proof of any custody changes. The other parent has a chance to respond. If you and the other parent agree on a new amount, you can stipulate to it in writing and the judge will sign it. If you disagree, a hearing will be held.
If income drops temporarily — a few months of reduced hours — the court may not recalculate. The change needs to be substantial and likely to continue. If a parent deliberately quits a job to avoid support, the court can impute income based on their earning capacity, which may result in a higher support order, not a lower one.
Frequently Asked Questions
Does California child support include college expenses?
No. The formula covers support until the child turns 18 or graduates high school, whichever is later. College costs are not included in the standard calculation. However, parents can agree in writing to pay for college, and a judge can order it in some cases, but this requires a separate agreement or court order beyond the child support formula.
What if one parent is self-employed or has irregular income?
The court averages self-employment income over two to three years using tax returns and business records. If income is highly variable — such as commission-based work or seasonal employment — the court may use an average or may impute income based on the parent's capacity. You will need to provide documentation: tax returns, profit-and-loss statements, and bank records.
Can the child support amount be changed if one parent remarries?
Remarriage itself does not trigger a recalculation. The formula is based only on the biological or adoptive parents' income, not a stepparent's income. However, if a parent's own income changes as a result of remarriage — for example, they reduce work hours because a spouse now earns more — that income change can be grounds for recalculation.
What happens if a parent's income is below minimum wage or they are unemployed?
If a parent is unemployed and actively seeking work, the court may use minimum wage as the basis for imputed income, or it may use their prior earning history. If a parent is disabled or unable to work, the court considers that, but support obligations do not disappear. The amount may be very low, but it is rarely zero unless the parent has no income and no capacity to earn.
Is the child support amount the same if parents share custody 50-50?
Not necessarily. Even with equal custody time, if one parent earns significantly more than the other, the higher earner pays support to the lower earner. The formula still applies; the custody split just changes the percentage. Two parents earning $40,000 and $80,000 with equal custody will result in a support order, because the income is unequal.