SupportSplit's Glossary of Child Support Terms
Every term used in the SupportSplit calculator, defined with references to the California Family Code and federal tax law. Click any statute citation to read the full text on the California Legislature's website.
A
Add-on expenses
Additional child-related costs that are divided between parents on top of the base guideline support amount. Mandatory add-ons include work-related childcare and uninsured health care for the children. Discretionary add-ons include educational expenses, extracurricular activities, and travel costs for visitation. Add-ons are allocated in proportion to each parent's net disposable income, adjusted by the support amount.
FC §4062 · See also: Childcare costs, Net Disposable Income, Add-on allocation
Add-on allocation
The method used to divide add-on expenses between parents. Under the proportional method (FC §4061(c)), each parent's net disposable income is first adjusted by the support amount: the payor's net is reduced and the receiver's net is increased. The adjusted incomes determine each parent's percentage share of the add-on costs.
FC §4061(c) · See also: Add-on expenses
Above-the-line deductions
Adjustments to gross income that are taken before arriving at adjusted gross income (AGI). These include HSA contributions, student loan interest, educator expenses, self-employment tax, and pre-2019 alimony. They reduce taxable income on both federal and California returns (except HSA, which is federal only).
26 USC §62 · See also: HSA contributions, Gross income
B
Best interest of the child
The standard used by California courts in all custody and support decisions. The court considers the child's health, safety, and welfare, the nature of contact with both parents, and any history of abuse. This standard governs departures from guideline support.
Bonus and commission income
Variable compensation such as bonuses, commissions, profit sharing, and RSU vests. Courts may include historical averages in gross income or issue a Smith-Ostler order requiring a percentage of future bonuses as additional support.
FC §4058(a) · See also: Smith-Ostler order, Gross income
C
Child multiplier
The guideline formula produces a base amount for one child. For additional children, the base is multiplied by a statutory factor: 1.6 for 2 children, 2.0 for 3, 2.3 for 4, and 2.5 for 5. Support does not scale linearly because many child-rearing costs are shared across siblings.
FC §4055(b)(4) · See also: Guideline formula
Child support paid (other cases)
Support obligations for children from other relationships, paid under existing court orders. These are deducted from net disposable income before computing guideline support for the current case.
FC §4059(e) · See also: Hardship deductions
Childcare costs
Costs of childcare related to employment or reasonably necessary education or training for employment skills. This is a mandatory add-on, meaning the court must order it when these costs exist. Childcare costs are divided between parents in proportion to their adjusted net incomes.
FC §4062(a)(1) · See also: Add-on expenses
Children's health insurance (add-on)
The cost of health insurance premiums for the children. This is a mandatory add-on under FC §4062(a)(2). Note: the portion each parent pays as a personal deduction under FC §4059(d) is different from the proportional allocation of the total cost here. A parent who carries insurance for the children gets credit for their share.
FC §4062(a)(2) · See also: Health insurance, children
Community property
Property acquired during marriage, which is presumed to belong equally to both spouses. Relevant to support because community property income (such as rental income from jointly owned property) is included in gross income, and the division of community assets at separation can affect each parent's financial situation.
D
Date of separation
The date on which one spouse communicated the intent to end the marriage, accompanied by conduct consistent with that intent. This date affects property characterization, support duration, and financial obligations. Income earned after separation is separate property.
Deduction impact
A feature of the SupportSplit calculator that shows how each individual deduction changes the monthly support amount. Adding a deduction to the higher earner typically reduces support, while adding one to the lower earner may increase it. This helps both parties understand which inputs have the most effect on the result.
FC §4059 · See also: Net Disposable Income
Deferred sale of residence
When the court orders that the family home not be sold immediately, typically to allow children to remain in the home. The economic benefit to the custodial parent (living in a home partially owned by the other parent) may be considered when determining support.
Dependency exemption allocation
The court may allocate the right to claim a child as a dependent for federal tax purposes to either parent, regardless of physical custody. This affects each parent's tax liability and therefore their net disposable income.
26 USC §152 · See also: Filing status
Departure from guideline
A court order for support that differs from the guideline amount. The guideline figure is presumptively correct, so the court must make specific findings to justify a departure. Common reasons include extraordinarily high income, a parent's voluntary unemployment, or special needs of the child. The requesting party bears the burden of proof.
FC §4057 · See also: Presumptively correct
E
Earning capacity
The income a parent could reasonably earn based on their education, marketable skills, work experience, and the availability of employment in their community. Courts may use earning capacity instead of actual income when a parent is voluntarily unemployed or underemployed. The court considers whether the unemployment is in good faith (e.g., a parent returning to school) or an attempt to reduce support obligations.
FC §4058(b) · See also: Imputed income
Educational / special needs
Costs related to a child's educational or other special needs. This is a discretionary add-on, which the court may order at its discretion. Examples include tutoring, private school tuition, therapy, and special equipment.
FC §4062(b)(1) · See also: Add-on expenses
Epstein credits
Reimbursement to a spouse who used separate property funds to pay community debts after the date of separation. Relevant to support because Epstein claims can affect the net financial position of each party during proceedings. Named after Marriage of Epstein (1979) 24 Cal.3d 76.
FC §2640 · See also: Date of separation, Watts charges
F
Filing status
Tax filing status used to determine applicable tax brackets, standard deduction amount, and credit phaseouts. For guideline child support calculations, Married Filing Separately (MFS) is the default. This is specified in FC §4059(a) and applies even if the parents file jointly in practice.
FC §4059(a) · See also: Standard vs. itemized deductions
401(k) / 403(b) / TSP
Employer-sponsored retirement plan contributions. These reduce federal and California taxable income as pre-tax payroll deductions, which lowers the taxes computed in the net disposable income calculation. The contribution amount is not subtracted again from NDI, because its benefit is already reflected in the lower tax figures. Mandatory retirement contributions (such as CalPERS) are treated similarly.
FC §4059(c) · See also: Net Disposable Income, Mandatory retirement
G
Gavron warning
A court admonition to a supported spouse (typically in spousal support orders) that they are expected to become self-supporting within a reasonable period. While primarily a spousal support concept, it can indirectly affect child support if the supported parent's imputed income changes as a result. Named after Marriage of Gavron (1988) 203 Cal.App.3d 705.
FC §4320(l) · See also: Imputed income, Spousal support
Gross income
Total income from all sources before taxes and deductions. Includes salary, wages, commissions, bonuses, rents, dividends, pensions, interest, trust income, Social Security benefits, unemployment insurance, disability insurance, and all other income. Self-employment income is included after business expenses. The definition is intentionally broad: if it's income, it's likely included.
FC §4058(a) · See also: Net Disposable Income, Imputed income, Bonus income
Guideline formula
CS = K × [HN − (H%)(TN)]. This is the statewide uniform formula for computing child support in California. K is the income allocation factor. HN is the higher earner's net disposable income (after taxes). H% is the higher earner's parenting time (timeshare %). TN is total net disposable income of both parents. The formula is mandatory: the court must use it unless specific grounds for departure exist under FC §4057.
FC §4055(a) · See also: K factor, Net Disposable Income, Presumptively correct
H
Hardship deductions
Deductions from net disposable income for extraordinary circumstances: uninsured catastrophic losses, extraordinary health expenses, or minimum basic living expenses for children from other relationships who reside with the parent. Subject to the cap in FC §4071(b): the court shall not reduce support to a level that leaves the obligor with more net income than the obligee.
FC §4071, FC §4070 · See also: Child support paid (other cases)
Health insurance, children
Monthly premiums a parent pays for health insurance covering the children. This is deducted from that parent's income when computing net disposable income. Separately, the total cost of children's health insurance is also treated as a mandatory add-on under FC §4062(a)(2), where it is allocated proportionally between parents.
FC §4059(d) · See also: Add-on expenses, Children's health insurance (add-on)
Health insurance, self only
Monthly premiums a parent pays for their own health insurance coverage. This is a post-tax deduction from net disposable income. It is not an add-on expense because it covers the parent, not the child.
FC §4059(d) · See also: Health insurance, children
High earner / extraordinary high income
When the payor's income is high enough that guideline support would exceed the children's reasonable needs, the court may depart from guideline. There is no fixed dollar threshold. The court looks at the actual needs of the children and the standard of living during the marriage.
FC §4057(b)(3) · See also: Departure from guideline
HSA contributions
Health Savings Account contributions. Deductible on the federal return (above-the-line deduction) but not deductible on the California return. This is a common source of error in support calculations. The correct treatment: HSA reduces federal tax only and does not reduce California tax.
26 USC §223 · See also: Above-the-line deductions, Health insurance
I
Imputed income
Income the court attributes to a parent who is unemployed or underemployed. The court considers the parent's education, marketable skills, work history, efforts to find work, and the availability of opportunities in their community. Income will not be imputed to a parent who is caring for a child of very young age, or where the cost of childcare would offset the income earned.
FC §4058(b) · See also: Gross income, Earning capacity
K
K factor
The income allocation factor in the guideline formula. K is computed in two steps: first, a base fraction (K ratio) is determined from the combined net disposable income using the statutory income band table. Then, the fraction is multiplied by a parenting time adjustment (1 + H% when the higher earner has less than 50% time, or 2 - H% when they have more). K increases as parenting time approaches 50/50, which is why the relationship between custody time and support is not linear.
FC §4055(b)(3) · See also: Guideline formula, K-factor income bands
K-factor income bands
The statutory table used to compute the base K fraction from combined net disposable income. Updated by SB 343 (effective September 2024). The five bands are: $0 to $2,900 (variable formula), $2,900 to $5,000 (variable formula), $5,000 to $10,000 (flat 25%), $10,000 to $15,000 (variable), and above $15,000 (variable). Higher combined income generally produces a lower K fraction, meaning a smaller percentage of the income differential goes to support.
FC §4055(b)(3) · See also: K factor
L
Low-income adjustment
When the obligor's net disposable income falls below $2,929/month (in 2026, derived from California minimum wage at 40 hours/week), the court may reduce guideline support. The reduction is proportional: as net income approaches zero, the adjustment increases. This protects low-income obligors from support orders that would leave them below subsistence.
FC §4055(b)(7) · See also: Net Disposable Income
M
Mandatory retirement contributions
Required contributions to employer-sponsored pension plans, such as CalPERS, CalSTRS, or federal FERS. These are pre-tax deductions that reduce taxable income. Unlike voluntary 401(k) contributions, mandatory retirement is not discretionary and cannot be used strategically to reduce support.
FC §4059(c) · See also: 401(k) / 403(b) / TSP
Modification of support
Either parent may request a modification of child support at any time upon a showing of changed circumstances. Common grounds include a material change in either parent's income, a change in parenting time, a child aging out, or a change in the needs of the child. There is no minimum waiting period.
Mortgage interest deduction
Interest paid on a qualified home mortgage, deductible as an itemized deduction on both federal and California returns. Limited to interest on up to $750,000 of acquisition debt (for loans originated after December 15, 2017). This is one of the most common reasons a parent's itemized deductions exceed the standard deduction.
26 USC §163(h) · See also: Itemized deductions
Move-away case
A case in which the custodial parent seeks to relocate a significant distance, typically affecting the existing parenting time arrangement. If the move is approved and parenting time changes, guideline support will change as a result. The primary custodial parent has a presumptive right to move, but the court balances this against the child's best interest and the noncustodial parent's relationship with the child.
FC §7501 · Marriage of LaMusga (2004) 32 Cal.4th 1072 · See also: Parenting Time
N
Net Disposable Income (after taxes)
The income figure used in the guideline formula. Computed by taking gross income and subtracting: federal income tax, California state income tax, Social Security tax, Medicare tax, California SDI, and allowable deductions such as health insurance premiums, union dues, existing support orders, and hardship deductions. Pre-tax retirement contributions (401(k), IRA) reduce net disposable income indirectly through lower taxes, not through a direct subtraction.
FC §4059 · See also: Gross income, 401(k)
O
Obligor / obligee
The obligor is the parent who pays child support. The obligee is the parent who receives it. In most cases, the higher earner with less parenting time is the obligor. However, in some parenting time arrangements, the lower earner can be the obligor if they have significantly more custody time.
P
Presumptively correct
The guideline support amount is presumed to be the correct amount of child support. Either parent may rebut this presumption, but the burden is on the party seeking a different amount to demonstrate that applying the guideline would be unjust or inappropriate in the specific case. The court must state its reasons for any departure on the record.
FC §4057(a) · See also: Departure from guideline
R
Retroactive support
Child support ordered back to the date of filing, or in some cases, back to the date of separation. California courts may order retroactive support to the date the requesting parent filed a motion. This means delays in filing can result in lost support for the receiving parent.
S
SALT cap
The federal cap on the state and local tax deduction (Schedule A). For 2026, the base cap is $40,400 per OBBBA, phasing down to $10,000 for MAGI above $505,500 at a 30% reduction rate. MFS filers have half the cap ($20,200). California has no state-level SALT cap, so the full amount of state and local taxes is deductible on the California return.
OBBBA (Pub. Law 119-21) · See also: Itemized deductions
Smith-Ostler order
An order requiring the payor to pay a percentage of bonus, commission, or other variable income as additional child support on top of the base guideline amount. Used when a parent has significant income that fluctuates and is difficult to predict. Named after Marriage of Ostler and Smith (1990) 223 Cal.App.3d 33. The percentage is typically based on the marginal guideline rate at the payor's income level.
FC §4055 · Marriage of Ostler and Smith (1990) 223 Cal.App.3d 33 · See also: Bonus income
Spousal support
Court-ordered support paid by one spouse to the other. Temporary (pendente lite) spousal support is often calculated using county-specific guidelines that are local practice formulas, not codified statutes. Permanent spousal support is governed by the factors in FC §4320. Spousal support paid reduces the payor's income available for child support and increases the recipient's income.
Standard vs. itemized deductions
For tax purposes, each parent uses either the standard deduction or their itemized deductions, whichever produces the greater tax benefit. Itemized deductions include mortgage interest, state and local taxes (subject to the SALT cap on the federal return), property taxes, and charitable contributions. The SupportSplit calculator automatically compares both methods and uses whichever produces the higher deduction, separately for federal and California returns.
26 USC §63 · See also: SALT cap, Filing status, Mortgage interest
Subsequent partner income
Income of a parent's new spouse or nonmarital partner. Generally not considered in calculating child support. However, it may indirectly affect the calculation if the new partner reduces the parent's living expenses (e.g., shared housing costs), effectively increasing the parent's available income.
Support termination
Child support ends when a child turns 18, or at age 19 if the child is still a full-time high school student and is not self-supporting. Support also terminates upon the child's marriage, emancipation, death, or entry into active military duty. For multiple children, support steps down as each child ages out.
T
Travel for visitation
Reasonable travel expenses necessary for a child to spend time with both parents. This is a discretionary add-on that the court may order. It is most relevant when parents live far apart and travel costs are significant.
FC §4062(b)(2) · See also: Add-on expenses
U
Union dues
Mandatory union membership dues paid by a parent. Deducted from net disposable income as a post-tax deduction under FC §4059. Only mandatory dues qualify; voluntary professional association fees generally do not.
V
Voluntary unemployment / underemployment
When a parent deliberately reduces their income to avoid or reduce support obligations. The court may impute income based on earning capacity. Legitimate reasons for reduced income (illness, caring for a young child, pursuing education in good faith) may be considered. The burden of showing that unemployment is voluntary is on the party alleging it.
FC §4058(b) · See also: Imputed income, Earning capacity
W
Watts charges
A claim for reimbursement when one spouse has exclusive use of a community property asset (typically the family home) after the date of separation without paying the other spouse for that use. Relevant to support because Watts charges can affect the financial picture presented to the court. Named after Marriage of Watts (1985) 171 Cal.App.3d 366.
FC §2640 · See also: Epstein credits, Date of separation