What software do California courts use to calculate child support?

California courts use DissoMaster and XSpouse software which implement the exact CA guideline formula. Our calculator uses the same formula for estimates. For court purposes, hire an attorney to run official calculations.

Can a California judge deviate from the guideline child support amount?

Yes, under Family Code §4057, courts can deviate in limited circumstances: deferred home sale, significant asset wealth, unjust application, or high-income cases where guideline exceeds children's needs. Deviation is rare and must be on the record.

How does time-share percentage affect California child support?

Time-share (H%) is critical in the CA formula CS = K[HN - (H%)(TN)]. When the higher earner has more custody time, H% increases and support decreases. This creates a financial incentive that courts account for when evaluating custody.

Are California bonuses and stock options included in child support income?

Yes. California includes all income: salary, bonuses, commissions, RSU vesting, stock options, rental income, and business income. Irregular income is typically averaged over recent years. Large bonuses may trigger a child support true-up.

What are California hardship deductions for child support?

California allows hardship deductions under Family Code §4071 for minimum basic living expenses for other children you support, catastrophic losses, and extraordinary expenses. These reduce net disposable income and potentially lower support, but require court approval.

California Child Support Calculator

Estimate CA guideline support using the post-SB 343 formula (effective 9/1/2025): CS = K[HN − (H%)(TN)] with net-income K-factors and $2,929 low-income adjustment threshold.

Updated April 2026 Family Code §4055 (post-SB 343) Private — runs in your browser

Parent 1 Monthly Gross Income

Before taxes and deductions

Parent 2 Monthly Gross Income

Before taxes and deductions

Number of Children

Higher Earner's Time with Children %

H% in CA formula

Parent 1 Monthly Deductions

Union dues, mandatory withholding

Parent 2 Monthly Deductions

Health Insurance Premium

Monthly premium for children

Retirement Contributions

401k, 403b (higher earner)

CA Guideline Child Support (Monthly)

$853/mo

Base CS (Formula)$704/mo

K Factor36%

Higher Earner Net$4,736/mo

Total Net Disposable$7,959/mo

CA guideline formula per Family Code §4055 (post-SB 343, effective 9/1/2025): CS = K[HN − (H%)(TN)] using net disposable income. CA courts use the Judicial Council Guideline Calculator; DissoMaster was decertified March 2025.

Advanced Calculator

Time-share percentage impact chart, high-income deviation scenarios, and year-by-year CA guideline projection.

+ Open Advanced Calculator

CA Guideline Inputs

Higher Earner Annual Income

Lower Earner Annual Income

Number of Children

Higher Earner Time-Share %

CA Guideline CS = K[HN − (H%)(TN)]

$2,250/mo

K factor0.25

HN (monthly)$12,500

TN (combined)$17,500

Annual Total$27,000

Higher Earner Time-Share % vs. Monthly Support

H% Time-Share	Monthly CS	Annual	vs. 0%
0%	$3,125/mo	$37,500	$0
10%	$2,688/mo	$32,250	−$438
20% ← you	$2,250/mo	$27,000	−$875
30%	$1,813/mo	$21,750	−$1,313
40%	$1,375/mo	$16,500	−$1,750
50%	$938/mo	$11,250	−$2,188
60%	$500/mo	$6,000	−$2,625
70%	$63/mo	$750	−$3,063
80%	$0/mo	$0	−$3,125
90%	$0/mo	$0	−$3,125

Professional Simulator

Full CA income breakdown (W-2, SE, RSUs, rental, stock options), CA state/SDI tax, add-ons, what-if scenarios, and 20-year lifetime projection.

+ Open Professional Simulator

Higher Earner Income — Total: $182,000/yr

W-2 / Salary

Self-Employment

Bonuses / RSUs

Rental Income

Stock Options

401k / Retirement Contr.

Union Dues / Other Deductions

Lower Earner Income — Total: $55,000/yr

W-2 / Salary

Self-Employment

Bonuses

Custody & Add-Ons

Children

Higher Earner Time-Share %

Health Insurance (child)/mo

Work-Related Childcare/mo

Educational Costs/mo

CA Full Guideline Analysis

$3,088/mo

HE Net Disposable

Gross: $182,000/yr

Federal tax: −$33,023

CA state/SDI: −$18,746

SE tax: −$4,239

Retirement: −$6,000

NDI: $119,992/yr ($9,999/mo)

Support Breakdown

Base CS: $1,814/mo

Health ins.: +$255/mo

Childcare: +$874/mo

Education: +$146/mo

Total: $3,088/mo

HE Income Share72.8%

Annual Total$37,060

% of HE NDI30.9%

HE Time-Share20%

How California Child Support Works in 2026

California codifies child support in Family Code §4055, one of the most mathematically precise formulas in the United States. In September 2025, Senate Bill 343 rebuilt the formula — moving from gross-income to net-income inputs, expanding the definition of income, and tightening add-on allocation rules. Every new order or modification filed on or after September 1, 2025 uses the post-SB 343 framework.

Court software note: California courts now use the Judicial Council Guideline Calculator and licensed Family Law Software. DissoMaster — long the de facto standard — was decertified in March 2025 and is no longer acceptable for official court filings.

The Guideline Formula (§4055)

The official algebraic statement:

CS = K × [HN − (H%) × TN]

CS = Monthly child support amount
K = Combined-income factor × per-children multiplier
HN = Higher earner's net disposable monthly income
H% = Higher earner's approximate time-share with the children
TN = Total net disposable income (both parents combined)

The K Factor — Post-SB 343

K is no longer a flat lookup by number of children. It is the product of two statutory components:

1. Combined-income factor (§4055(b)(3)(A))

TN ≤ $800/mo: factor = 0.20 + TN/16,000
$801 ≤ TN ≤ $6,666/mo: factor = 0.25 + TN/160,000
$6,667 ≤ TN ≤ $10,000/mo: factor = 0.10 + 1,000/TN
TN > $10,000/mo: factor = 0.12 + 800/TN

2. Per-children multiplier (§4055(b)(3)(B))

1 child: 1.0×
2 children: 1.6×
3 children: 2.0×
4 children: 2.3×
5 children: 2.5×
6 children: 2.625×
7 children: 2.75×
8+ children: 2.813×–2.86×

Low-Income Adjustment (2026)

Per §4055(b)(7), if the paying parent's net monthly disposable income is below $2,929 (the 2026 threshold, tied to California minimum wage of $16.90 × 173.33 hours), support is reduced on a sliding scale. This threshold shifted sharply upward from the pre-SB 343 level (~$1,500) to protect low-wage parents.

Net Disposable Income Components

Per §4059, net disposable income is gross income minus:

Federal and state income taxes
FICA (Social Security 6.2% + Medicare 1.45%)
California SDI (0.9% in 2026, wage base $176,100)
Mandatory union dues and retirement contributions
Health insurance premiums for the parent (not the children's portion — that is an add-on)
Court-ordered prior child or spousal support for other relationships
Hardship deductions under §4071 (minimum living expenses for other children, catastrophic loss)

Add-On Allocation — Now Mandatory Pro-Rata

Under SB 343, add-ons for uninsured health costs, childcare, and educational expenses must be allocated in proportion to each parent's net income share, not 50/50. This was discretionary before September 2025; courts must now apply pro-rata unless they make a written finding for deviation.

Worked Example — 2026 Post-SB 343

Parent 1 earns $8,000/mo gross. Parent 2 earns $5,000/mo gross. Two children. Parent 1 (higher earner) has 35% time-share. Health insurance premium for children: $250/mo.

Parent 1 Net (HN)~$5,340/mo

Parent 2 Net (LN)~$3,340/mo

Total Net (TN)~$8,680/mo

Income factor (§4055(b)(3)(A))0.10 + 1,000/8,680 = 0.215

Children multiplier (2)1.6×

K0.344

CS = 0.344 × [5,340 − 0.35 × 8,680]~$792/mo

P1 income share (pro-rata)61.5%

+ Health insurance add-on (61.5% × $250)~$154/mo

Total Monthly Support~$946/mo

The higher earner pays despite having 35% time with the children because their net income — combined with the children's needs — exceeds the time-share offset.

Official Sources & Legal References

Frequently Asked Questions

What changed with SB 343 on September 1, 2025? ▼

SB 343 reengineered the California child support formula in three ways: (1) the K-factor now uses net disposable income, not gross, which changes every result above roughly $3,500/mo net; (2) the Low-Income Adjustment threshold rose to $2,929/mo (tied to minimum wage); (3) add-on allocation for childcare, health, and educational expenses is now mandatory pro-rata by income share, not discretionary 50/50. Orders issued before 9/1/2025 use the pre-SB 343 gross-income K table; new orders and modifications use the current formula.

What software do California courts use in 2026? ▼

California courts use the Judicial Council Guideline Calculator and certified Family Law Software (FLS). DissoMaster — the long-time industry standard — was decertified in March 2025 and is no longer acceptable for official filings. Our calculator implements the statutory formula directly from Family Code §4055 and is intended for estimation, not for court filings.

Can a California judge deviate from the guideline amount? ▼

Yes, but rarely. Under Family Code §4057, courts can deviate if: the sale of a family home is deferred, a parent has significant non-income wealth, application would be unjust in a specific case, or in high-income cases where guideline exceeds the children's actual needs. Deviation requires written findings on the record. The presumption of correctness applies — the burden is on the party seeking deviation.

How does time-share affect California child support? ▼

Time-share (H%) is the higher earner's approximate share of primary physical responsibility. When the higher earner has more time, H% increases and support decreases. This creates a mathematical incentive that courts are aware of — they evaluate the best interests of children independently. 50/50 shared care with similar incomes typically produces near-zero child support; large income gaps produce support even with equal time.

Are bonuses, RSUs, and stock options included in income? ▼

Yes. Under §4058 (amended by SB 343), California defines income broadly: salary, bonuses, commissions, RSU vesting value, exercised stock options, rental income, business income, severance pay, lottery winnings, veterans' non-need-based benefits, and military BAH/BAS. Irregular income is typically averaged over recent years. Large one-time bonuses may trigger a child support "true-up" motion by the other parent.

What is the Low-Income Adjustment in 2026? ▼

Per §4055(b)(7), if the paying parent's net monthly disposable income is below $2,929 (the 2026 threshold tied to CA minimum wage $16.90/hr), the guideline support amount is reduced on a sliding scale. At very low income, the court may presume zero support. The threshold adjusts annually with minimum wage — check California DCSS for current year.

When to Consult a California Family Law Attorney

This calculator produces a useful estimate, but California child support is one of the most litigated areas of family law. Consult a licensed California attorney if your case involves: combined net income above $10,000/mo (high-income deviation questions), self-employment or business ownership (income imputation), pre-SB 343 orders subject to modification, significant assets generating non-wage income, or disputes about time-share percentage. Only a certified family law specialist can run official Judicial Council Calculator numbers for court filings.