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Child Support in California

Free calculator, modification rules, arrears interest, and 50/50 custody guide for California — 2026.

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Child Support Calculator
Estimate payments using California's Income Shares
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Modification Checker
Does your income change qualify?
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Arrears Calculator
Past-due support with 10% interest
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50/50 Custody Guide
Does equal custody eliminate support?

California Child Support Facts — 2026

Formula modelIncome Shares
Income basisBoth parents' income
Support ends at age18
Modification threshold20% income change
Arrears interest rate10% per year
Official agencyCalifornia Child Support Agency ↗
California uses a complex algebraic formula (CS = K[HN-(H%)(TN)]) based on both parents' net disposable income and custody time. Updated by SB 343 in 2024 to use net income calculations.

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