Child Support Calculation FAQ

California uses a statewide guideline formula to calculate child support, codified in Family Code Section 4055. This formula is mandatory and creates a rebuttable presumption that the amount calculated is the correct amount of child support to be ordered. The formula considers both parents' net disposable income, the percentage of time each parent has physical custody of the children (timeshare), and other relevant factors to determine a fair support amount.

The basic formula is: CS = K[HN - (H%)(TN)], where CS is the child support amount, K is the total amount of both parents' income allocated for child support, HN is the high earner's net monthly disposable income, H% is the approximate percentage of time the high earner has primary physical responsibility for the children (expressed as a decimal), and TN is the total net monthly disposable income of both parties. Most practitioners and courts use computerized programs such as DissoMaster or XSpouse to calculate child support using this complex formula. The formula is designed to ensure that children maintain the same standard of living they would have enjoyed if their parents remained together.

Under Family Code Section 4058, income for child support purposes includes all sources of income from whatever source derived. This broad definition encompasses wages, salary, commissions, bonuses, self-employment income, rental income from properties, dividends, interest, royalties, trust income, annuities, workers' compensation benefits, unemployment insurance benefits, disability insurance benefits, social security benefits, and spousal support actually received from a different relationship. The statute's "whatever source derived" language means courts will look at virtually any form of economic benefit received by a parent.

The definition also includes income from stock options, capital gains (though courts have discretion on how to treat these), lottery winnings, gifts and prizes that constitute recurring income, partnership distributions, and any other form of compensation. Courts examine tax returns, pay stubs, bank statements, and other financial documents to identify all income sources. If a parent is intentionally unemployed or underemployed, the court may impute income based on earning capacity rather than actual earnings. The inclusive definition ensures that children receive support commensurate with the parent's true ability to pay, regardless of how creative the parent might be in structuring their compensation or hiding income.

Family Code Section 4059 specifies the exclusive list of allowable deductions from gross income to arrive at net disposable income for child support purposes. These deductions include federal and state income taxes actually payable (based on proper withholding allowances), federal insurance contributions act taxes (FICA/Social Security and Medicare), state disability insurance contributions, mandatory union dues and retirement contributions required as a condition of employment, health insurance premiums for the parent and the children of the marriage or relationship, child support or spousal support actually being paid pursuant to a court order from a different relationship, and certain hardship deductions authorized under Family Code Section 4071.

Importantly, many common expenses are NOT deductible when calculating child support. These non-deductible items include voluntary retirement contributions beyond mandatory amounts, mortgage payments, credit card payments, car payments, private school tuition, charitable contributions, and general living expenses. Courts strictly limit deductions to those specifically enumerated in the statute to ensure the maximum amount of income is available for child support. Parents sometimes mistakenly believe they can deduct all their living expenses, but the law intentionally restricts deductions to protect children's financial interests. The calculation focuses on gross income with limited deductions, rather than disposable income after all bills are paid, ensuring adequate support for children's needs.

Yes, Family Code Section 4057 allows courts to deviate from the guideline formula, but only under specific circumstances and with detailed findings. The guideline amount creates a rebuttable presumption that it is the correct amount of child support. A court can order a different amount when it determines that application of the formula would be unjust or inappropriate in the particular case, consistent with the principles set forth in Family Code Section 4053. When deviating from the guideline, the court must state in writing or on the record the following information: the amount of support that would have been ordered under the guideline formula, the reasons the amount ordered is consistent with the best interests of the children, and the reasons that application of the guideline would be unjust or inappropriate.

Deviations are not granted lightly. The court must make specific findings explaining why the guideline amount would be unjust or inappropriate and how the deviated amount better serves the children's best interests. Simply disagreeing with the guideline amount or finding it inconvenient is insufficient. The deviation must be based on the special circumstances outlined in Family Code Section 4057(b). Additionally, stipulated agreements between parents for an amount different from the guideline must meet the same standards and receive court approval, and parents must be informed of their rights and the guideline amount before agreeing to a deviation. Courts maintain significant discretion but must exercise it within the statutory framework designed to protect children's interests.

Family Code Section 4057(b) lists several circumstances that may justify deviation from the guideline formula. One common situation involves parents with substantially equal timeshare where one parent has significantly higher or lower income than the other, potentially making the guideline amount inappropriate. Another scenario occurs when a parent is not contributing to the children's needs at a level commensurate with that parent's custodial time, which might justify increasing support despite the timeshare calculation. Courts may also deviate when application of the formula would result in a support amount that exceeds the actual needs of the children, particularly in very high-income cases where the guideline amount might provide a windfall beyond what is necessary for the children's welfare.

Additional grounds for deviation include cases where a child has special medical or other needs requiring a higher level of support than the guideline provides, situations where the sale of the family residence is deferred under Family Code Section 3800 and the rental value exceeds the mortgage payments (affecting the parents' respective abilities to pay support), and the increasingly common situation where a child has more than two parents as a result of modern family structures. Each deviation must be carefully analyzed and supported by evidence showing that the guideline amount would be unjust or inappropriate. The court must balance the needs of the children, the parents' financial circumstances, and the statutory preference for the guideline formula, ensuring any deviation genuinely serves the children's best interests rather than simply accommodating a parent's preferences.

Under Family Code Section 4058(a)(3), self-employment income means gross receipts minus ordinary and necessary expenses required to carry on the trade or business. This calculation differs significantly from tax calculations and requires careful scrutiny. Courts examine tax returns (particularly Schedule C for sole proprietors or K-1 forms for partnerships and S-corporations), profit and loss statements, business bank statements, and other business records to determine the actual income available for child support purposes. The key issue is distinguishing between legitimate business expenses that reduce income and personal expenses or tax strategies that should not reduce child support.

Depreciation deductions are particularly controversial in child support cases. While depreciation reduces taxable income on tax returns, it often does not represent actual cash leaving the business, so courts frequently add back depreciation to determine income available for child support. Similarly, courts examine whether the business is paying for personal expenses such as car payments, cell phones, travel, or meals that primarily benefit the parent personally rather than the business. Courts also consider whether a self-employed parent is taking an unreasonably low salary while retaining earnings in the business, and whether income is being diverted to family members or other entities to artificially reduce support obligations. The burden is on the self-employed parent to clearly document that deducted expenses are truly ordinary, necessary, and business-related rather than personal in nature.

California law requires certain additional expenses to be shared by both parents in addition to the basic guideline support amount calculated under Family Code Section 4055. Under Family Code Section 4062, these mandatory add-ons include childcare costs related to employment or to reasonably necessary education or training for employment skills, and the reasonable uninsured health care costs for the children. These expenses are not included in the base guideline calculation but must be allocated between the parents, typically in proportion to their net disposable incomes, as additional child support obligations.

Childcare costs include daycare, after-school care, and babysitting expenses that are necessary to allow a parent to work or obtain education or training that will lead to employment. Uninsured health care costs include medical, dental, vision, and other health-related expenses not covered by insurance, such as co-pays, deductibles, prescription medications, orthodontia, counseling, and other therapeutic services. The court must make specific orders regarding how these add-on costs will be paid, whether by direct reimbursement, inclusion in monthly support payments, or direct payment to providers. Parents typically exchange receipts and proof of payment, with the non-paying parent reimbursing their proportional share within a specified timeframe, often 30 days. These add-ons ensure that children's actual needs are met beyond the basic support amount.

Family Code Section 4062(a)(1) requires that childcare costs related to employment or reasonably necessary education or training for employment skills be shared by both parents as additional child support. The costs are divided between parents in proportion to their net disposable incomes as calculated for child support purposes. For example, if the combined net monthly disposable income of both parents is $10,000, and one parent earns $7,000 (70%) while the other earns $3,000 (30%), they would be responsible for 70% and 30% of childcare costs respectively. If monthly daycare costs $1,200, the higher-earning parent would pay $840 and the lower-earning parent would pay $360.

The parent incurring the childcare expense (usually the custodial parent who is arranging care while working) typically pays the provider directly and then submits receipts to the other parent for reimbursement of their proportional share. Courts may order specific reimbursement procedures, such as monthly exchange of receipts with payment due within 30 days. Some courts order the non-custodial parent's share to be included in the monthly child support payment, particularly when childcare costs are consistent and predictable. The childcare must be reasonable in cost and necessary for employment purposes. Luxury care or unnecessarily expensive options may be partially disallowed. Parents can also deduct children's health insurance premiums from income before calculating support, but must share uninsured medical costs as an add-on expense.

Family Code Section 4058(b) grants courts authority to impute income to a parent who is voluntarily unemployed or underemployed, meaning the court can base child support on what the parent could and should be earning rather than actual current earnings. When considering imputation, courts examine the parent's ability to work, work history, occupational qualifications, educational attainment, age, health, the local job market and availability of positions matching the parent's skills, and whether unemployment or underemployment is in good faith or designed to reduce child support obligations. Courts can impute income based on recent earnings, industry standards for someone with similar qualifications, or full-time minimum wage as a baseline.

However, imputation is not automatic. Before imputing income, courts must consider several factors: whether the parent is genuinely seeking employment but unable to find work despite reasonable efforts, whether physical or mental disabilities prevent the parent from working or limit earning capacity, whether the parent is incarcerated or institutionalized, whether the parent is caring for children of the relationship for whom childcare would be inappropriate or unavailable given the children's ages or special needs, and whether there are other legitimate reasons for reduced earnings. The party seeking to impute income bears the burden of proof. Courts must make specific findings supporting imputation, including the amount imputed and the basis for that determination. Imputation protects children from parents who intentionally reduce income to avoid support while respecting legitimate reasons for reduced earnings.

Timeshare, defined as the percentage of time each parent has physical custody of the children, is a critical component of the guideline formula under Family Code Section 4055. The formula uses the high earner's percentage of custodial time (H%) to adjust the support amount, recognizing that parents incur direct costs for children's expenses during their custodial periods. When one parent has the children most of the time (for example, 80% vs. 20%), that parent receives higher support from the other parent. As timeshare approaches equality (40-50% for each parent), the support amount decreases significantly because both parents are directly bearing expenses while children are in their care, reducing the need for support transfers.

Timeshare is calculated based on the number of overnight visits per year, with 365 total days divided between the parents. Courts typically use custody schedules, calendars, parenting plans, or testimony to determine the actual percentage. Even small changes in timeshare can substantially impact support, particularly when custody time is close to equal. For example, the difference between 45% and 50% timeshare can mean thousands of dollars annually. This creates incentive for disputes over the exact timeshare calculation. Courts must determine timeshare based on the actual parenting plan ordered, not on occasional deviations or what parents hope will happen. The calculation requires precision because the formula is sensitive to timeshare changes, especially in the 35-50% range where the support obligation changes most dramatically with small shifts in custodial time.