California Family Code §4053 outlines the principles guiding child support. Both parents share a mutual responsibility to support their children according to their circumstances and station in life. It is in the child's best interest to be financially supported by both parents, and children should share in the standard of living of both parents. Child support may also improve the custodial parent's standard of living, which benefits the child.
Coordinating financial support with parenting arrangements works best when paired with our child custody and visitation guidance so both time and money align with your family’s needs.
Guideline Formula (Combined Income Approach)
California uses a statewide uniform guideline formula, not specifically called the "Income Shares Model." The formula is similar in concept to income shares approaches used in many other states, as it considers the combined income of both parents and their respective parenting time.
The statutory formula (Family Code §4055) is:
CS = K [HN – (H%) (TN)]
Where:
- CS = Child support amount
- K = Combined income allocation factor
- HN = High earner's net monthly disposable income
- H% = Percentage of time the high earner has primary physical responsibility for the child
- TN = Total net monthly disposable income of both parents
The formula ensures that children receive a fair share of both parents' income as if the parents were living together.
Parenting Time (Timeshare)
Parenting time directly affects the guideline amount. The more time a higher‑earning parent spends with the child, the lower the guideline child support obligation becomes. This is because that parent is directly covering a larger share of the child's daily expenses during their custodial time.
When parenting time is contested, review our modification overview for tips on updating orders that no longer reflect current schedules.
Determining the Amount of Support
California courts use a statewide child support calculator to apply the guideline formula. The major factors influencing support include:
- Number of children entitled to support
- Percentage of parenting time each parent has (timeshare)
- Each parent's net monthly disposable income
- Tax filing status of each parent
- Deductions for other child/spousal support obligations
- Health insurance costs and union dues
The calculator is available through the California Child Support Services website.
Guideline Child Support
The amount determined by the formula is called the guideline child support amount. Under Family Code §4057, this amount is presumed to be correct and will normally be ordered by the court.
Deviating from the Guideline Amount
A court may order more or less than the guideline amount only if applying the guideline would be unjust or inappropriate in a particular case. The court must state:
- The guideline amount calculated
- The reason for the deviation
- Why the ordered amount is in the best interest of the child
Common reasons the court might deviate include:
- The parties have a valid written agreement approved by the court (per Family Code §4065)
- The child has special medical or educational needs requiring additional support
- The paying parent's income is extraordinarily high, making guideline support excessive
- Parents have similar parenting time but very different incomes
- Other circumstances where the guideline would be unjust or inappropriate
Parental Agreements
Parents may agree to a different child support amount, subject to court approval. However:
- Child support arrears cannot be waived.
- If the agreed amount is below the guideline, the court must find that both parties were informed of their rights, entered the agreement voluntarily, and that the amount is in the child's best interest.
- If the child is receiving public assistance, the local child support agency must approve the agreement, and the order cannot be below guideline (§4065(c)).
Parents negotiating both support and alimony can coordinate outcomes by consulting our spousal support resource before finalizing a settlement.
Health Insurance (Medical Support)
In addition to base child support, the court usually includes medical support provisions. One or both parents may be ordered to provide health insurance if available at a reasonable cost. Generally, employer-provided coverage is presumed reasonable. A plan may be considered unreasonable if its cost exceeds a modest portion (commonly around 5%) of a parent's gross income.
If one parent provides health insurance, the support calculation may be adjusted to reflect that contribution.
When courts deviate from guideline support
Judges may order a different amount if applying the formula would be unjust or inappropriate. Common reasons to deviate include extraordinarily high incomes, special medical needs, or shared parenting arrangements that make the guideline number unrealistic. Any deviation must still meet the child’s best interests and requires explicit findings on the record.
- Substantial disparity between parental incomes alongside nearly equal time shares.
- Significant travel costs for visitation or schooling.
- Extraordinary health care or educational expenses.
Health insurance and add-ons
Support orders typically address health coverage and supplemental expenses beyond the base guideline number. Parents may be required to maintain group insurance if available at reasonable cost, reimburse uninsured medical bills, and share child care costs necessary for work or education.
If circumstances shift after an order is entered, see the modification and enforcement guide for the process to recalibrate support.
Child Support Add-Ons
California law allows certain expenses to be added to the base child support order under Family Code §§4062–4063.
Mandatory Add-Ons
- Uninsured Health Care Expenses – Costs for reasonable medical, dental, or vision services not covered by insurance.
- Child Care Costs – Necessary expenses for a parent's employment, education, or training.
These are typically divided equally between the parents unless the court orders a different allocation.
Discretionary Add-Ons
Courts may order additional add-ons based on the child's needs and parents' ability to pay, such as:
- Private or Special Schooling – For educational or special needs
- Extracurricular Activities – When the child has a history of participation or special talent
- Travel Expenses – When significant travel is required for visitation or custody exchanges
Termination of Child Support
Child support in California generally continues until the child turns 18 years old. If the child is still in high school, unmarried, and living with a parent, support continues until the child turns 19 or graduates, whichever comes first (Family Code §3901).
Support obligations also end if the child becomes emancipated, marries, or joins the military. Parents may voluntarily agree to support a child beyond these ages (e.g., college expenses).
Legal Assistance
The child support system can be complex, with numerous factors affecting calculation and enforcement. Consulting an experienced California family law attorney can help ensure that the correct guideline is applied, possible deviations are identified, and appropriate add-ons are considered.