California Child Support Calculator (2025)

How California Calculates Child Support

California uses a unique Income Shares Model governed by Family Code Sections 4050 through 4076. Unlike many states that rely on simple lookup tables, California employs a complex algebraic formula that considers both parents' net monthly disposable income, the percentage of time each parent has primary physical custody (the timeshare), and the number of children requiring support.

The California guideline formula is designed to ensure that children benefit from both parents' income in proportion to each parent's ability to contribute. The formula is presumed to be correct under California law, meaning courts will apply it unless a party demonstrates that applying the formula would be unjust or inappropriate under the specific circumstances of the case.

California's approach differs from most other states because it integrates timeshare directly into the formula rather than applying a separate parenting-time adjustment. This means that the amount of time each parent spends with the child has a direct, mathematical impact on the support obligation from the outset of the calculation.

Net Monthly Disposable Income

Before applying the formula, California first determines each parent's net monthly disposable income. This is calculated by starting with gross income and subtracting specific mandatory deductions allowed under Family Code Section 4059:

• Federal and state income taxes based on the parent's actual tax filing status and allowable deductions
• FICA contributions (Social Security and Medicare taxes)
• Mandatory retirement contributions required as a condition of employment
• Mandatory union dues
• Health insurance premiums for the parent only (children's premiums are handled separately)
• State disability insurance
• Costs of raising children from other relationships the parent is legally obligated to support
• Hardship deductions permitted under Family Code Section 4071

The California Guideline Formula Explained

The California child support formula may look intimidating at first glance, but each variable has a clear meaning:

How the Formula Works in Practice

The expression inside the brackets, [HN - (H%)(TN)], calculates the higher earner's net income minus their share of the total income based on timeshare. When the higher earner has more timeshare (more custody time), the value of (H%)(TN) increases, which reduces the amount inside the brackets and therefore reduces the child support obligation. This reflects the principle that a parent who spends more time with the child is already directly contributing to the child's expenses during that time.

The K factor then multiplies this result to determine the final guideline amount. A higher K factor (which increases with more children) means a larger portion of the adjusted income is allocated to child support. The result of the formula, CS, is the monthly guideline child support amount that the higher earner pays to the lower earner.

DissoMaster and Computer Calculation Programs

In practice, California family law attorneys and courts rarely perform the guideline calculation by hand. Instead, they use specialized computer programs that automate the formula and account for the complex tax calculations involved. The most widely used programs include:

• DissoMaster — The most popular child support calculation software in California, used by the majority of family law attorneys and many courts. DissoMaster handles the full guideline formula, tax calculations, add-on expenses, and generates detailed reports.
• Xspouse — Another approved program that performs the same calculations as DissoMaster with a different user interface.
• SupporTax — A third approved program option available to practitioners.

Our calculator above provides a simplified estimate based on the guideline formula. For the most accurate calculation, attorneys will run your specific numbers through an approved program that accounts for your exact tax situation, filing status, itemized deductions, and other factors that affect net disposable income. If you are going through a child support proceeding, your attorney will generate a DissoMaster report as part of the process.

Income Types Considered in California

California Family Code Section 4058 defines income broadly for child support purposes. The court considers virtually all sources of recurring income, including but not limited to:

• Wages, salary, and tips from all employment
• Commissions and bonuses, typically averaged over a reasonable period
• Self-employment income (business revenue minus legitimate expenses)
• Rental income from real property
• Dividends, interest, and capital gains
• Pension and retirement income
• Social Security benefits
• Unemployment and disability insurance benefits
• Workers' compensation benefits
• Spousal support (alimony) received from another relationship
• Trust income
• Annuity payments

Income Imputation

When a parent is unemployed or underemployed, California courts have the authority to impute income to that parent. Under Family Code Section 4058(b), the court may consider the parent's earning capacity rather than their actual income. To impute income, the court considers:

• The parent's ability and opportunity to work
• The parent's education, skills, and work history
• The job market in the parent's geographic area
• The availability of suitable employment opportunities
• Whether the parent is voluntarily underemployed or unemployed

Courts will not impute income to a parent who is unable to work due to disability, who is caring for a very young child (typically under age 5), or who has a legitimate reason for reduced employment. However, if the court finds that a parent is intentionally earning less to avoid child support, it can base the calculation on what that parent could be earning.

Deviation Factors in California

While the guideline formula creates a rebuttable presumption of correctness, California Family Code Section 4057(b) allows courts to deviate from the guideline amount when specific factors are present:

• Extraordinarily high income: When a parent's income is so high that the guideline amount exceeds the child's reasonable needs, the court may cap the support at a level appropriate to the child's actual needs and reasonable standard of living.
• Non-contributing parent: If a parent is not contributing to the child's needs commensurate with their custodial time (for example, receiving timeshare credit but not actually exercising custody), the court may adjust the support amount.
• Special educational needs: Children with exceptional educational requirements, such as gifted programs or private schooling that is in the child's best interest, may warrant additional support.
• Children's travel expenses: When parents live far apart, significant travel costs for visitation may justify a deviation.
• Seasonal fluctuations: If a parent has seasonal employment with large income swings, the court may adjust the formula to account for irregular earning patterns.
• Both parents' agreement: Parents may stipulate to a different amount, but the court must find that the agreed amount adequately meets the child's needs and is not a result of coercion or uninformed consent.

Any deviation from the guideline must be accompanied by a specific finding by the court explaining why the guideline amount would be unjust or inappropriate. The party seeking a deviation bears the burden of proof.

Self-Employment Income in California Child Support

Self-employment income presents unique challenges in California child support cases. Unlike W-2 wage earners whose income is easily verified, self-employed parents may have significant control over how they report income and expenses. California courts employ several strategies to ensure accurate income assessment:

Determining True Self-Employment Income

The court starts with gross business receipts and subtracts only legitimate, necessary business expenses. California courts are authorized to:

• Add back depreciation and other non-cash deductions that do not represent an actual out-of-pocket expense
• Scrutinize home office deductions and personal vehicle use for potential personal expenses disguised as business costs
• Review entertainment and travel expenses for personal benefit
• Examine owner's compensation relative to industry standards for comparable positions
• Consider retained business earnings as available income when the parent controls the business

Courts may require the self-employed parent to produce detailed business records, tax returns for multiple years, profit-and-loss statements, bank records, and other financial documentation. In some cases, a forensic accountant may be appointed to examine the parent's true income and earning capacity.

New Spouse Income in California

One of the most common questions in California child support cases is whether a parent's new spouse's income will affect the calculation. Under California Family Code Section 4057.5, the general rule is clear: a new spouse's income is not considered in determining child support.

The rationale is straightforward: a stepparent has no legal obligation to support another person's children. The biological or adoptive parents remain solely responsible for child support.

Exceptions to the General Rule

While rare, there are limited circumstances where a new spouse's income may become relevant:

• Extreme hardship cases: If excluding the new spouse's income would result in extreme hardship to the children, the court may consider it
• Tax filing impact: Remarriage changes tax filing status (married filing jointly vs. single), which can indirectly affect the net disposable income calculation
• Lifestyle evidence: A new spouse's income may be used to demonstrate that a parent's actual standard of living is higher than their individual income would suggest, potentially supporting income imputation arguments

Modifying Child Support in California

California child support orders can be modified at any time when there is a material change of circumstances since the last order was made. Unlike some states that require a minimum percentage change in income or a waiting period, California has no statutory threshold — any material change can be the basis for a modification request.

Common Grounds for Modification

• Job loss or significant income reduction (involuntary)
• Substantial income increase by either parent
• Change in timeshare or custody arrangement
• Change in the number of children requiring support (child reaching age 18/19)
• Change in health insurance costs or availability
• Change in childcare expenses
• Incarceration of the obligor (with some limitations)
• Disability affecting earning capacity

The Modification Process

To request a modification, you must file a Request for Order (Form FL-300) with the court that issued the original child support order. Key points about the process:

1. File the FL-300 form along with a current Income and Expense Declaration (Form FL-150)
2. Serve the other parent with the filed documents at least 16 court days before the hearing
3. Attend the hearing where the court will determine whether a material change exists
4. If modification is granted, the new amount is effective as of the date the motion was filed, not retroactively

It is important to file for modification promptly when circumstances change. Until you file, the existing order remains in full effect, and unpaid amounts accrue as a judgment that cannot be forgiven by the court.

Child Support and Taxes in California

Understanding the tax treatment of child support is essential for both paying and receiving parents:

• Child support payments are not tax-deductible for the paying parent under federal or California state tax law
• Child support payments are not taxable income for the receiving parent
• The child tax credit and dependency exemption generally go to the custodial parent (the parent with whom the child lives for more than half the year), unless the custodial parent signs Form 8332 releasing the exemption to the non-custodial parent
• Head of household filing status is available to the parent who provides more than half the cost of maintaining a home for the child
• The Earned Income Tax Credit (EITC) may be claimed by the custodial parent if they meet income requirements

These tax consequences are already partially built into the California guideline formula, which calculates net disposable income after accounting for each parent's estimated tax obligations. The approved computer programs (DissoMaster, Xspouse, SupporTax) perform detailed tax calculations to determine each parent's actual net disposable income.

Other State Child Support Calculators

California Child Support FAQ