Support in California (2026)

California’s Time-Share Guideline Formula

California’s approach to child support is built around an algebraic guideline formula that is unlike any other state’s. Codified in Family Code Section 4055, the formula simultaneously accounts for each parent’s income and the percentage of time each parent spends with the child — making the time-share arrangement one of the most financially consequential decisions in a California custody case.

The guideline formula is expressed as:

CS = K [HN - (H%)(TN)]

Where CS is child support, K is a factor based on the number of children and the amount of time the higher earner spends with the children, HN is the higher earner’s net monthly disposable income, H% is the percentage of time the higher earner has the children, and TN is the total net monthly disposable income of both parents.

In practical terms, this means that small changes in the time-share arrangement can produce significant changes in the support obligation. A parent who has the children 30% of the time will generally pay more support than a parent who has them 40% of the time, even if both parents earn the same income. This mathematical reality makes custody and support negotiations deeply intertwined in California — more so than in states that use a simpler percentage-of-income model.

Because the formula involves several interrelated variables, most attorneys and courts rely on software programs such as DissoMaster or Xspouse to run the calculation. These programs produce a printout showing the inputs, the guideline amount, and the factors used. You can get a preliminary estimate of what your obligation might look like by using our child support calculator.

How California Calculates Child Support

California uses an income shares model built around the guideline formula codified in Family Code Section 4055. Unlike simpler percentage-of-income approaches used in a few other states, California’s formula is algebraic and accounts for multiple variables simultaneously.

The core calculation considers each parent’s net disposable income and the percentage of time each parent spends with the child. Net disposable income is gross income minus certain mandatory deductions, including state and federal taxes, health insurance premiums, mandatory union dues, and mandatory retirement contributions. The formula then weights these figures against the time-sharing arrangement so that the parent with less custodial time generally pays support to the parent with more.

For a deeper explanation of how income shares models work nationally, see our guide on how child support is calculated.

Key Factors in the California Guideline Formula

The guideline formula under Family Code Section 4055 weighs the following:

• Each parent’s net monthly disposable income. This includes wages, salary, commissions, bonuses, rental income, business income, and in some cases imputed income if a parent is voluntarily underemployed.
• Time-sharing percentage. The percentage of time each parent has physical custody directly affects the calculation. A parent who has the children 40% of the time will have a different obligation than one who has them 20% of the time.
• Tax filing status and exemptions. The formula accounts for which parent claims the children as dependents for tax purposes.
• Mandatory payroll deductions. Only legally required deductions reduce income for guideline purposes — voluntary 401(k) contributions, for example, are generally not subtracted.

Courts may also consider hardship deductions under Family Code Section 4071, such as extraordinary health expenses or uninsured catastrophic losses.

Deviating from the Guideline Amount

California law creates a rebuttable presumption that the guideline amount is correct. However, Family Code Section 4057 allows deviation in special circumstances. A court may order a different amount when:

• A parent’s income is extraordinarily high, and the guideline amount would exceed the child’s reasonable needs
• A parent is not contributing to the child’s housing costs
• The parties have stipulated to a different amount, provided the child’s needs are adequately met
• Special medical, educational, or travel expenses warrant an adjustment

Any deviation must be accompanied by a written finding explaining why the guideline amount would be unjust or inappropriate.

Modifying or Terminating Child Support

Either parent can request a modification of child support at any time by showing a material change of circumstances. Common grounds include a significant change in either parent’s income, a change in the time-sharing arrangement, or a change in the child’s needs. Job loss, disability, or a substantial raise can all qualify.

Child support in California generally continues until the child turns 18, or 19 if the child is still a full-time high school student and is not self-supporting. Support also terminates if the child marries, enters the military, or is legally emancipated.

Enforcement of Child Support Orders

California takes child support enforcement seriously. The Department of Child Support Services (DCSS) can pursue a range of remedies against a parent who fails to pay, including:

• Wage garnishment (income withholding orders)
• Interception of tax refunds
• Suspension of driver’s licenses, professional licenses, and passports
• Liens on real property and bank accounts
• Contempt of court proceedings, which can result in fines or jail time

Unpaid child support accrues interest at 10% per year under California law, and arrears cannot be retroactively reduced — a court can only modify support going forward from the date a modification request is filed.

Spousal Support (Alimony) in California

California distinguishes between temporary spousal support and long-term (permanent) spousal support. Temporary support is awarded during the divorce proceedings and is typically calculated using a local county formula — often around 40% of the higher earner’s net income minus 50% of the lower earner’s net income, though this varies by county.

Long-term spousal support is governed by Family Code Section 4320, which lists 14 factors the court must consider. These include:

• The marketable skills of the supported party and the job market for those skills
• The extent to which the supported party’s earning capacity was impaired by periods of unemployment during the marriage devoted to domestic duties
• The standard of living established during the marriage
• The duration of the marriage
• The ability of the supporting party to pay, taking into account earning capacity, earned and unearned income, assets, and standard of living
• Each party’s needs based on the marital standard of living
• Each party’s assets and debts
• The age and health of both parties
• Documented evidence of domestic violence
• The tax consequences to each party
• The balance of hardships to each party
• The goal that the supported party be self-supporting within a reasonable period of time

Duration of Spousal Support

For marriages lasting fewer than 10 years, the general expectation is that spousal support will last approximately half the length of the marriage. A five-year marriage, for example, would typically result in a support order lasting around two and a half years.

For marriages of 10 years or longer — classified as “long-term marriages” under the Marital Duration Rule — there is no presumed termination date. The court retains jurisdiction indefinitely unless both parties agree otherwise or a court later orders termination. This does not mean support will last forever, but it means neither party can assume it will end on a fixed date without a court order.

When to Seek Legal Guidance

Child support and spousal support disputes in California can involve substantial sums and complex calculations. If you are facing a support dispute — whether you are seeking support or expect to pay it — understanding the guideline formula and the factors that influence judicial discretion is essential. If you need help evaluating your situation, consider scheduling a free consultation to discuss your options with an experienced family law professional.

Statutes referenced: California Family Code Sections 4050-4076 (child support), Sections 4320-4326 (spousal support).

Frequently Asked Questions

How is child support calculated in California?

California uses an income shares model with an algebraic guideline formula under Family Code Section 4055. The formula considers each parent’s net disposable income (gross income minus taxes, health insurance, mandatory retirement, and union dues) and the percentage of time each parent has physical custody. The parent with less custodial time generally pays support to the parent with more. Most attorneys use software like DissoMaster to run the calculation.

How long does child support last in California?

Child support continues until the child turns 18, or 19 if the child is still a full-time high school student and not self-supporting. Support also terminates if the child marries, enters the military, or is legally emancipated.

What interest accrues on unpaid child support in California?

Unpaid child support accrues interest at 10% per year under California law. Arrears cannot be retroactively reduced — a court can only modify support going forward from the date a modification request is filed. The Department of Child Support Services can pursue wage garnishment, tax refund interception, license suspension, property liens, and contempt proceedings.

How does California distinguish between temporary and long-term spousal support?

Temporary support is awarded during divorce proceedings and is typically calculated using a local county formula — often around 40% of the higher earner’s net income minus 50% of the lower earner’s net income. Long-term support is governed by Family Code Section 4320, which requires the court to weigh 14 factors including earning capacity, standard of living, duration of the marriage, and domestic violence history.

How does the time-share percentage affect child support in California?

The time-share percentage is one of the most significant variables in California’s guideline formula. Small changes in parenting time can produce meaningful changes in the support amount. For example, moving from a 70/30 time-share to a 60/40 arrangement could reduce the support obligation substantially, even with no change in either parent’s income. This is why custody and support negotiations in California are often closely linked.

Can the court impute income to a voluntarily underemployed parent?

Yes. Under Family Code Section 4058, if a parent is voluntarily unemployed or underemployed, the court may calculate support based on that parent’s earning capacity rather than actual income. The court considers the parent’s work history, qualifications, job opportunities, and any barriers to employment. This prevents a parent from artificially reducing their support obligation by choosing not to work or by taking a lower-paying job.

How This Guide Was Researched

This guide is based on California Family Code Sections 4050-4076 (child support guidelines), Section 4055 (the guideline formula), Section 4057 (deviation from guidelines), and Sections 4320-4326 (spousal support factors). The time-share formula explanation was verified against DissoMaster calculation methodology and published Judicial Council training materials. Enforcement procedures were confirmed against Department of Child Support Services (DCSS) published resources. Filing procedures were verified against current Judicial Council forms FL-150 (Income and Expense Declaration) and FL-155 (Financial Statement).

Sources and Legal References

This guide is based on publicly available legal information and official sources, including:

• California Family Code §§ 4050-4076 (child support guidelines), § 4055 (guideline formula), § 4057 (deviation factors), § 4058 (income definition and imputation)
• California Family Code §§ 4320-4326 (spousal support factors), § 4071 (hardship deductions)
• Department of Child Support Services (DCSS) enforcement procedures and published guidelines
• Judicial Council Forms FL-150, FL-155, FL-342 (income and expense declarations, child support information)

Official California Resources

• California Courts — Self-Help Guide
• California Department of Child Support Services
• California Divorce Forms

Additional California Resources

• Spenn Law — Family Law Resources for Santa Clara & San Benito Counties

For more about how we research our guides, see our editorial policy and sources methodology.

Related Guides

Learn more about related family law topics:

• Child Support and Self-Employment in California
• Spousal Support Calculator Factors in California
• Divorce in California
• Child custody in California
• How child support is calculated
• Modifying child support
• Child support calculator
• How to file for child support