Child support

Child support in California — the complete guide.

California uses a statutory guideline formula to set child support. The formula isn't optional — judges must follow it unless very specific exceptions apply.

The California guideline (Family Code §4055) is the single most-litigated number in family law because two seemingly small inputs — net disposable income and timeshare percentage — drive everything. Understanding how each works is half the battle.

1
The formula
CS = K[HN − (H%)(TN)]. CS is the support amount for one child. K is an adjustment factor based on combined income. HN is the high earner's net monthly income. H% is the high earner's timeshare. TN is total net monthly income. Multiple-child amounts use multipliers: ×1.6 for 2 kids, ×2.0 for 3, ×2.3 for 4, ×2.5 for 5.
Cal. Family Code §4055
2
What counts as income
Almost everything: salary, bonuses, commissions, self-employment income, rental income, investment income, pensions, disability and unemployment benefits, even gifts that are recurring. The court can also impute income to a parent who is voluntarily unemployed or underemployed.
Cal. Family Code §4058
3
Net disposable income
Gross income minus mandatory deductions: federal and state taxes, FICA, mandatory union dues, mandatory retirement contributions, health insurance premiums, and any existing court-ordered spousal or child support paid for other children.
Cal. Family Code §4059
4
Timeshare
The percentage of time the child spends with the higher-earning parent. Calculated by total annual hours, not days. A 40% timeshare reduces support meaningfully; a true 50/50 schedule reduces it more. Disputes over timeshare are common and can shift the support number by hundreds of dollars per month.
5
Mandatory add-ons
On top of base support, the court must add 50% of childcare costs related to employment or education and 50% of uninsured medical, dental, and vision costs. Discretionary add-ons can include educational expenses and travel for visitation.
Cal. Family Code §4062
6
Modification
Either parent can request a modification when there's a 'material change of circumstances' — a job loss, a raise, a change in custody, or a new child. There is no minimum waiting period to request a change.
7
Enforcement
Unpaid child support accrues interest at 10% per year and cannot be discharged in bankruptcy. The Department of Child Support Services (DCSS) can garnish wages, intercept tax refunds, suspend driver's and professional licenses, and place liens on property.
Cal. Family Code §17400 et seq.