Sources and scope: the legal statements below were compared with the linked California statutes, court rules, and court or agency material. This is general legal information, not advice about a specific case.
The statewide formula is the presumptive starting amount
Family Code §4053 treats support as both parents' responsibility and seeks to let children share in each parent's standard of living. The amount produced by the guideline is presumed correct. A judge who orders something different must rely on a statutory reason and make the required findings.
For one child, §4055 states CS = K[HN − (H% × TN)]. HN is the higher earner's monthly net disposable income; H% is that parent's approximate share of primary physical responsibility; TN is the parents' combined monthly net disposable income; and K is the income-allocation factor adjusted for H%.
| Symbol | Meaning | What often goes wrong |
|---|---|---|
| CS | Monthly basic child support | Treating §4062 add-ons as though they were already included |
| HN | Higher earner's monthly net disposable income | Entering gross pay or ordinary paycheck take-home |
| H% | Higher earner's approximate share of physical responsibility | Using a custody label instead of the actual pattern of responsibility |
| TN | Both parents' combined monthly net disposable income | Missing one parent's tax treatment or statutory deductions |
| K | Income-allocation factor adjusted for H% | Using an old income band or a flat percentage |
Paycheck take-home is not necessarily net disposable income
Section 4058 broadly defines annual gross income. Wages, bonuses, commissions, business profit, interest, dividends, rent, pensions, and some benefits can count. Under specified conditions and when consistent with a child's best interests, the court may use earning capacity instead of the income a parent is actually receiving.
Section 4059 then allows particular deductions to reach net disposable income: actual federal and state tax liability, FICA or self-employment contributions, mandatory retirement, qualifying health premiums, support actually paid under qualifying orders, necessary job expenses, and permitted hardships. Subtracting a guessed tax percentage from salary does not recreate that calculation.
- Convert annual and irregular income to monthly figures consistently.
- Use the tax status and dependents the law requires, not the most favorable hypothetical return.
- Claim only deductions allowed by §4059; normal household spending is not automatically deductible.
- Separate business revenue and ordinary, necessary business expenses from personal spending.
- Run a new calculation when income, tax law, parenting responsibility, or add-on costs change.
K changes with income and time; the child count changes the final multiplier
The one-child income fraction changes across five combined-net-income bands. It is multiplied by 1 + H% when the higher earner's H% is 50% or less, or by 2 − H% when it is greater than 50%. After the one-child amount is found, a separate multiplier applies for two through ten children.
When the higher earner has more than half the physical responsibility, the signed equation can point the payment in an unexpected direction. The parent with fewer overnights is not automatically the payer; the sign of the statutory result determines direction.
| Combined monthly net disposable income (TN) | Base fraction before the H% adjustment |
|---|---|
| $0–$2,900 | 0.165 + TN ÷ 82,857 |
| $2,901–$5,000 | 0.131 + TN ÷ 42,149 |
| $5,001–$10,000 | 0.25 |
| $10,001–$15,000 | 0.10 + 1,499 ÷ TN |
| Over $15,000 | 0.12 + 1,200 ÷ TN |
H% follows actual physical responsibility, not the words on the custody order
H% is the higher earner's approximate share of primary physical responsibility compared with the other parent. 'Joint custody' alone supplies no number. The regular calendar, school and child-care periods, holidays, vacations, and who is actually responsible during those periods can all matter.
If different children follow different schedules, §4055 uses the average of their approximate percentages. Keep the calendar behind any percentage you enter. It is a support input, not a custody ruling or a prediction of the schedule a judge will order.
The low-income adjustment creates a range for the judge to consider
Section 4055 compares the obligor's monthly net disposable income with monthly gross earnings from full-time work at the statewide minimum wage. At $16.90 an hour in 2026, that comparison is $2,929.33 a month. Falling below it creates a rebuttable presumption that the obligor is entitled to an adjustment.
That does not erase support. The statute defines the largest permitted reduction, and the court decides whether the lowest end would be unjust after considering the guideline principles and the effect on both parents' net incomes. Showing the permitted range makes that choice visible.
Calculate basic support first, then deal with add-ons
Section 4062 generally requires additional support for child care actually incurred for work or reasonably necessary job training and for reasonable uninsured health costs. Child care is not added again if it was specifically included in the guideline calculation. The judge may also order education or special-needs costs and travel for parenting time.
Section 4061 calculates basic support first. For add-on allocation, the paying parent's net disposable income is reduced by basic support, but the receiving parent's net is not increased by the payment. Qualifying expenses are then divided in proportion to those adjusted net incomes unless a party requests, or the court orders, another division. A 50/50 split is not the statutory default.
| Expense | Statutory treatment | Calculation note |
|---|---|---|
| Work or qualifying-training child care | Mandatory when actually incurred and not already included in the guideline | Allocated after basic support |
| Reasonable uninsured child health care | Mandatory | Receipts and the §4063 reimbursement procedure matter |
| Education or special needs | Discretionary | The judge decides whether to order it |
| Parenting-time travel | Discretionary | May be allocated as additional support |
A judge may deviate, and support does not always stop on the eighteenth birthday
A court may depart from the guideline only for a statutory reason and with the required findings. Examples can include an extraordinarily high earner whose formula amount exceeds the children's needs, a parent who does not contribute in proportion to custodial time, and specified shared-time situations. Even an agreement needs the child-support findings required by law; local child support agency approval may also be necessary in an agency case.
The ordinary duty generally ends at 18, but §3901 continues it for an unmarried 18-year-old who attends high school full time and is not self-supporting until grade 12 is complete or the child turns 19, whichever comes first. A documented medical condition can excuse the full-time-attendance requirement. Other law can require support for an adult child who cannot earn a living and lacks sufficient means, and parents may agree to support beyond the statutory duty.
The DCSS public guideline calculator remains online, but the Judicial Council's table—last updated April 22, 2026—lists it as decertified and not recertified for 2026–27. A live public page is not proof of certification. For a calculation intended for court, use a program on the current certified list or ask the local family law facilitator.
Questions readers often ask
Frequently asked questions
What is California's child support formula?
For one child, §4055 uses CS = K[HN − (H% × TN)]. It combines both parents' monthly net disposable income with the higher earner's approximate share of physical responsibility. A separate multiplier applies for two through ten children.
Does California use gross or net income?
The equation uses monthly net disposable income derived from statutory gross income and the deductions allowed by §4059. Ordinary take-home pay or a flat tax estimate may not be the right figure.
Does 50/50 parenting time eliminate child support?
No. Both parents' net incomes remain part of the equation. Equal time can still produce a payment when the parents have different incomes.
What is the 2026 low-income comparison?
It is $2,929.33 a month, based on full-time work at the $16.90 statewide minimum wage. Falling below it creates a possible adjustment range, not an automatic zero order.
Are child-care and uninsured medical costs included in basic support?
Generally, they are additional support. Qualifying child care actually incurred for work or job training is mandatory unless specifically included in the guideline calculation, and reasonable uninsured child health costs are mandatory. Other add-ons may be discretionary.
Can I use the DCSS public calculator for a court filing?
The calculator remains online, but the Judicial Council's current table lists it as decertified and not recertified for 2026–27. Use currently certified software or ask the local family law facilitator for a court-use calculation.
Sources used for this guide
Official sources
- California Family Code §3901 — Duration of support
Sets the ordinary age-18 end point and continued support for a qualifying high-school student until grade 12 is complete or age 19, whichever comes first.
- California Family Code §4053 — Guideline principles
States California's child-support policies, both parents' responsibility, and the presumption that guideline support is correct.
- California Family Code §4055 — Statewide formula
Contains CS = K[HN − (H% × TN)], the income bands in effect since September 1, 2024, child multipliers, payment direction, and the low-income adjustment.
- California Family Code §4057 — Presumption and deviations
Makes the guideline amount presumptively correct and identifies circumstances and findings that can support a different order.
- California Family Code §4058 — Annual gross income
Defines annual gross income, statutory exclusions, when earning capacity may replace actual income, and treatment of specified benefits.
- California Family Code §4059 — Net disposable income
Lists the deductions allowed when converting annual gross income to net disposable income.
- California Family Code §4061 — Allocating add-ons
Requires basic support to be calculated first, then allocates add-ons by adjusted net income unless another division is requested or ordered.
- California Family Code §4062 — Child-support add-ons
Identifies qualifying child care and uninsured health costs as mandatory additional support and education, special-needs, and visitation travel as discretionary add-ons.
- California Courts — Child support
Explains the information used for support, how long an order may last, modification, and help available from county facilitators.
- Judicial Council — Guideline support calculator status
Lists software certified for California court proceedings and shows the DCSS public calculator as decertified for 2026–27.
- California Child Support Services — Public calculator page
The public tool remains online and describes its result as an estimate. The separate Judicial Council status table determines whether a program is currently certified.
- California DIR — 2026 statewide minimum wage
Confirms the $16.90 statewide hourly minimum wage effective January 1, 2026.