How California Calculates Child Support
California uses the Income Shares model to determine child support obligations. This page explains the guidelines, formula, and key factors.
Model Type
Income Shares (algebraic formula: CS = K[HN - (H%)(TN)])
California uses an algebraic formula: CS = K[HN - (H%)(TN)], where K is a factor based on both parents combined income and number of children, HN is the high earner net disposable income, H% is the high earner time-share percentage, and TN is combined net disposable income. Time-share percentage directly affects support amount.
Income Basis & Definitions
net monthly disposable income (both parents)
Determines K factor in the guideline formula.
Source: §4055(b)(3) K factor table by number of childrenNet monthly disposable income as defined by Family Code §4059–§4060 (gross less taxes, mandatory deductions).
Source: §4059 gross income definitionNet monthly disposable income of the other parent.
Source: §4059 gross income definitionParenting Time Handling
Percentage of time each parent has physical custody (H%); directly used in guideline formula CS = K[HN - (H%)(TN)].
Source: §4055(b)(1)(D) approximate time-share percentageDeductions & Adjustments
Hardship deductions for extraordinary health expenses, uninsured catastrophic losses, or other qualifying children per §4071.
Source: §4071 hardship deduction categories