The Guideline Formula
California Family Code § 4055 sets the statewide child support formula. The formula takes into account:
- Each parent’s net monthly disposable income — gross income minus allowable deductions including taxes, mandatory union dues, health insurance premiums, and other court-ordered support obligations.
- The percentage of time the child spends with each parent — called the timeshare.
- The number of children being supported.
The formula is complex enough that California courts use certified software programs to run the numbers. The California Department of Child Support Services provides a free public calculator at childsupport.ca.gov/guideline-calculator/ — it is based on the same legal guidelines used in California courts and can give you a reasonable estimate of what a court might order in your case. Both parents are required to complete an Income and Expense Declaration (FL-150) providing verified financial information.
What Counts as Income
California Family Code § 4058 defines income broadly. It includes:
- Wages, salaries, and commissions.
- Self-employment income — gross receipts minus legitimate business expenses.
- Rental income.
- Unemployment and disability benefits.
- Pension and retirement income.
- Social Security benefits.
- Investment income — dividends, interest, capital gains.
- Workers’ compensation benefits.
Income also includes earning capacity — meaning if a court finds a parent is voluntarily unemployed or underemployed, the court can impute income based on what that parent could be earning. A parent cannot reduce their child support obligation simply by choosing to work less.
What Counts as a Deduction
Allowable deductions from gross income include:
- Federal and state income taxes based on the parent’s actual filing status.
- Social Security and Medicare taxes.
- Mandatory union dues.
- Health insurance premiums for the parent only.
- Existing court-ordered child or spousal support for other relationships.
- Certain job-related expenses.
How Timeshare Affects the Calculation
The percentage of time the child spends with each parent is one of the two most significant variables in the formula. More time with a parent generally reduces that parent’s support obligation — because they are directly bearing more of the child’s day-to-day costs during their parenting time.
Timeshare is calculated based on actual time — not just overnight visits. Courts look at the total number of hours per year each parent has primary responsibility for the child.
Deviating From Guideline Support
Courts are required to order guideline support in most cases. California Family Code § 4056 requires the court to make specific findings before ordering an amount different from the guideline. Permitted deviations include situations where both parents agree to a different amount in writing and the court finds the agreement is in the child’s best interests, where the guideline amount would be unjust or inappropriate in the particular case, or where a parent has an extraordinarily high income and the guideline amount exceeds the child’s needs.
Courts cannot deviate downward from guideline support simply because a parent claims they cannot afford it — inability to pay is addressed through the income imputation rules, not by departing from the guideline.
Add-On Expenses
California Family Code § 4062 requires courts to add certain expenses to the base guideline support amount. Mandatory add-ons include:
- Childcare costs related to employment or job training.
- Reasonable uninsured healthcare costs for the child.
Discretionary add-ons — which the court may order depending on the circumstances — include costs for the child’s education, special needs, and travel for visitation.
Modifying Child Support
Child support is not permanent. Either parent can request a modification when there is a material change in circumstances — a significant change in either parent’s income, a change in the child’s needs, or a substantial change in the timeshare arrangement.
A modification requires a court order. Parents cannot simply agree between themselves to change the amount without going back to court — an informal agreement is not enforceable and does not change the existing order.
Enforcing Child Support
California has aggressive child support enforcement mechanisms. The Department of Child Support Services can enforce support orders through wage garnishment, bank levies, tax refund intercepts, license suspension — including driver’s licenses and professional licenses — and passport denial for parents who are significantly behind.
Unpaid child support accrues interest at 10 percent per year under California Family Code § 4722 and does not go away — it cannot be discharged in bankruptcy.
Frequently Asked Questions
Can parents agree to their own child support amount?
Yes — but the agreement must be approved by the court and the court must find it is in the child’s best interests. A private agreement between parents that has not been entered as a court order is not enforceable through the court’s contempt powers.
What if the other parent is hiding income?
Underreporting income is common in child support proceedings, particularly for self-employed parents. Courts can subpoena bank records, tax returns, and business records. If a parent is found to be hiding income, the court can impute income based on lifestyle evidence and impose sanctions.
Does child support cover college expenses?
In California, child support obligations end when the child turns 18 and graduates from high school, or turns 19 — whichever comes first. California does not require parents to contribute to college expenses through child support, though parents can agree to do so voluntarily.
What if I lose my job — can I stop paying?
No. You must continue paying the existing order until a court modifies it. If you lose your job, file a request for modification immediately. Arrears that accumulate before the modification is granted are still owed in full.
Where can I estimate my child support amount?
The California Department of Child Support Services provides a free public calculator at childsupport.ca.gov/guideline-calculator/ — it uses the same formula California courts apply and can give you a baseline estimate before you go to court.
Does this apply outside California?
Child support calculation methods vary by state. California’s guideline formula is California-specific. Federal law under the Uniform Interstate Family Support Act governs enforcement of California orders in other states and vice versa.