California has used a single statewide uniform guideline since SB 343 took effect on September 1, 2024, replacing the old algebraic formula with the Family Code § 4055 approach. The calculation runs on each parent’s net disposable income after actually payable taxes — this tool applies 2026 federal tax parameters alongside 2025 California tax parameters, since the state hadn’t published its 2026 figures yet. A statutory low-income adjustment is shown as the range the law provides for, rather than a single hard-coded number.
Key facts
| Model | Statewide uniform guideline — Fam. Code §§ 4050-4076 (SB 343, operative 2024-09-01) |
|---|---|
| Income basis | Net disposable income with actually-payable taxes |
| Tax years used | Federal TY2026, California TY2025 |
| Low-income adjustment | Shown as the statutory range |
Official source: https://childsupport.ca.gov/guideline-calculator/
Custody arrangements covered
- The § 4055 formula (CS = K[HN − (H%)(TN)]) already accounts for each parent’s timeshare percentage directly
Frequently asked questions
Did California’s child support formula change recently?
Yes — SB 343 replaced the prior formula with a single statewide uniform guideline under Family Code § 4055, operative September 1, 2024.
What income does California child support use?
Net disposable income, meaning income after actually payable taxes rather than a flat estimated deduction.
Why does this calculator mix two tax years for California?
Because the state’s 2026 tax parameters weren’t published yet, this tool uses the latest fully official figures: federal tax-year 2026 rules alongside California’s 2025 tax-year figures.
Does California have a low-income adjustment?
Yes, the statute provides one; this calculator shows it as the statutory range rather than assuming a single value.
Update history
- — California went live under the statewide uniform guideline (Fam. Code §§ 4050–4076, SB 343, operative 2024-09-01), using net disposable income with each parent's actually payable taxes and the statutory low-income adjustment range.