Updated: 2026-06-11
Quick answer: California sets child support with a statewide formula (Family Code § 4055) that runs on both parents’ net disposable incomes and the share of time each has the children — not a flat percentage. Senate Bill 343, operative September 1, 2024, updated the formula’s K-factor brackets for the first time since 1992, raised the low-income threshold to roughly full-time minimum-wage earnings, and changed the default for add-on costs like childcare and uninsured medical from a 50/50 split to each parent’s share of income. The Department of Child Support Services runs the program, payments flow through the State Disbursement Unit, and support generally ends at 18 — or 19 if the child is still a full-time high school student. Use the state’s official Guideline Calculator for an estimate.
Legal disclaimer: This article is general information, not legal advice. Child support rules and amounts change, and your case can vary from the guideline. For your specific situation, consult a family-law attorney licensed in California.
California’s child support math is the most formula-driven in the country, and it changed in a meaningful way in 2024. The state doesn’t use a simple percentage or a lookup table — it runs both parents’ net incomes and parenting time through an algebraic formula. This guide explains how that formula works, what the 2024 changes did, and points to every official place to estimate, apply, pay, and manage a case.
One quick clarification before the details: child support is separate from spousal support, the California term for what many people call “alimony.” Spousal support is money paid to a former partner; child support is for the children, and the two are decided under different rules. This guide covers child support only.
Table of Contents
- How is child support calculated in California?
- What counts as income?
- How does parenting time affect child support?
- What changed in California child support under SB 343?
- How much is child support in California? A worked example
- Does California child support include childcare and medical costs?
- How do you apply for child support in California?
- How do you pay child support in California?
- How do you check your California child support balance online?
- How do you modify a California child support order?
- What happens if you don’t pay child support in California?
- How long does child support last in California?
- Official California child support resources
- Frequently Asked Questions
How is child support calculated in California?
California uses a single statewide guideline formula, set out in Family Code § 4055. Every court in the state starts from the same equation, which looks intimidating but rests on two common-sense ideas: how much the parents earn, and how much time the children spend with each.
The formula is CS = K (HN − (H% × TN)). Here’s what each piece means:
| Symbol | What it stands for |
|---|---|
| CS | The guideline child support amount (per month) |
| K | The fraction of both parents’ income set aside for support — it rises and falls with the income band |
| HN | The higher earner’s net monthly disposable income |
| H% | The share of parenting time the higher earner has with the children |
| TN | Both parents’ total net monthly disposable income combined |
In plain terms: the more the higher earner makes relative to the other parent, the larger the support; the more parenting time that higher earner has, the smaller it gets. Because the math is genuinely complex — the K-factor alone shifts across income brackets — almost no one computes it by hand. The state and the courts rely on certified software and the official calculator, and so should you. For more than one child, the guideline multiplies the one-child figure by a set factor (for example, 1.6 for two children, 2 for three).
What counts as income?
The formula runs on net monthly disposable income, not gross pay. You start with income from nearly every source — wages, salary, bonuses, commissions, self-employment income, rental and investment income, unemployment, and the like — and then subtract specific deductions listed in Family Code § 4059.
Those deductions include federal and state income tax, FICA or other mandatory retirement, mandatory union dues, health-insurance premiums, and any child or spousal support actually being paid under another order. What’s left is the net disposable income that drives the formula — which is why two parents with the same salary can have different net figures.
How does parenting time affect child support?
Heavily — parenting time is built directly into the formula as H%, the percentage of time the higher earner has primary physical responsibility for the children. As that parent’s timeshare goes up, the guideline amount comes down, because they are covering more of the children’s day-to-day costs directly.
This is why an accurate timeshare matters so much in California. A few percentage points of parenting time can move the monthly number, so parents often disagree about how overnights and daytime hours are counted. Our guide to how a 50/50 schedule affects support explains how an equal split changes the math.
What changed in California child support under SB 343?
Senate Bill 343, operative September 1, 2024, was the most significant overhaul of California’s guideline in more than three decades. Three changes matter most:
- The K-factor brackets were updated for the first time since 1992. The income bands that set how much of the parents’ income goes to support were recalibrated, which changes the guideline amount across income levels.
- The low-income adjustment was raised. The threshold that protects a lower-earning parent’s basic living expenses is now tied to roughly full-time earnings at the state minimum wage — in the neighborhood of $2,800 to $2,900 a month — instead of a fixed older figure, and courts now presume a qualifying low earner gets the adjustment.
- Add-on costs are now split by income, not 50/50. Under Family Code § 4061, expenses like childcare and uninsured medical care used to be divided equally by default. The new default divides them in proportion to each parent’s net income.
These changes apply to orders established or modified on or after September 1, 2024. An existing order keeps its current numbers until someone asks the court to recalculate — and because the formula shifted, many older orders now come out differently if recalculated.
How much is child support in California? A worked example
Because California uses an algebraic formula rather than a table, there’s no clean “this income equals this payment” shortcut — the K-factor, the net-income deductions, and the timeshare all interact. The honest answer is that the number comes from the calculator, not from a rule of thumb.
What you can predict is the direction each input pushes:
| If this goes up… | …the guideline amount tends to |
|---|---|
| The higher earner’s net income | Rise |
| The gap between the two parents’ incomes | Rise |
| The paying parent’s share of parenting time | Fall |
| The number of children | Rise (by a set multiplier) |
| Deductions like taxes and health premiums | Fall (they lower net income) |
So a parent who earns far more than the other and sees the children only every other weekend will land at the high end; two parents with similar incomes and a near-equal schedule will land low, sometimes close to zero. For an actual figure, use the California Child Support Guideline Calculator, the state’s official tool, which applies the current K-factor and the 2024 changes. Treat any result as an estimate — the court has the final say and can deviate under Family Code § 4057.
Does California child support include childcare and medical costs?
Yes, as add-ons that sit on top of the base guideline amount. California splits two categories:
- Mandatory add-ons — work-related childcare and the children’s reasonable uninsured health-care costs. Courts must order these.
- Discretionary add-ons — things like a child’s special education needs or travel for visitation, which a court may order.
The big 2024 change is how they’re divided. The default is now proportional to each parent’s net income rather than a flat 50/50 split, so a parent who earns 70% of the combined income generally covers 70% of the childcare bill. Health insurance for the child is also required when it’s available at reasonable cost. Keep clear records of every shared expense and reimbursement — our guide to documenting co-parenting expenses explains how to track them so they hold up if there’s a dispute.
How do you apply for child support in California?
California child support is run by the Department of Child Support Services (DCSS) through a local child support agency (LCSA) in each county, and opening a case is free. Either parent or a guardian can apply, whether or not a court order already exists — the agency can locate the other parent, establish parentage, set an order, and enforce it.
You can open a case online through California Child Support Services, or work with your county’s local agency. Parents who already have an order from a divorce or parentage case can enroll it with DCSS so payments are processed and tracked by the state. If your case is part of a broader custody filing, our overview of how the custody court process works explains how the pieces fit together.
How do you pay child support in California?
All California child support payments are processed through the State Disbursement Unit (SDU), which by federal law handles 100% of the state’s child support payments. You don’t pay the other parent directly — paying through the SDU creates the official record that the payment was made.
The most common method is an income withholding order (wage assignment), where the amount comes straight out of the paying parent’s paycheck. Parents can also pay on their own through the methods DCSS offers, including electronic payment, by mail, and other options listed on the payer dashboard. Always include your case number so the payment is credited correctly, and don’t rely on a mailed check arriving the same day — wage withholding is the most reliable way to stay current.
How do you check your California child support balance online?
DCSS offers a self-service portal called Customer Connect, where both parents can view payment history, check balances, contact a caseworker, and update contact information 24/7. You register at Customer Connect using your Participant ID (PAR ID), which appears on a support check or billing statement, and then create a PIN.
The portal is the quickest way to confirm a payment posted or check a balance without calling. For help by phone, California runs a statewide child support line at 1-866-901-3212, and your county’s local child support agency handles in-person questions.
How do you modify a California child support order?
A California order can be changed when there’s been a change in circumstances since the last order — most commonly a meaningful change in either parent’s income, a change in the parenting schedule, a job loss, or a change in the children’s needs. Unlike some states, California has no fixed percentage trigger; you show the court that something material has changed.
You can ask your local child support agency to review the order or file a request with the court yourself. One caution that trips people up: support doesn’t change on its own when your income drops. The existing amount keeps running, and arrears keep building, until a new order is entered — so request a review promptly rather than waiting. If you and the other parent agree on a new number, a written stipulation approved by the court is the fastest route; our guide to reaching a custody agreement without a court fight is a good starting point.
What happens if you don’t pay child support in California?
California enforces support aggressively, and DCSS can use most of these tools without a new court hearing. When payments fall behind, the state can:
- Withhold income directly from wages and other payments
- Suspend a driver’s license, professional license, or occupational license
- Intercept state and federal tax refunds and lottery winnings
- Place liens on property and bank accounts, including levying accounts
- Report the debt to credit bureaus
- Deny or revoke a U.S. passport when arrears reach $2,500
- Pursue the case in court, including a contempt action that can carry jail time
Unpaid California support also accrues interest at 10% per year by law, and it can’t be erased in bankruptcy. If you genuinely can’t pay, request a modification rather than letting a balance grow — interest on a large arrears figure adds up quickly.
How long does child support last in California?
California ends support earlier than many states and does not require parents to pay for college. Under Family Code § 3901, the duty runs until the child turns 18 — extended to 19, or until the child finishes 12th grade, whichever comes first, if at 18 the child is still a full-time high school student and not self-supporting. A few points to keep in mind:
- No college obligation: California does not make parents pay for college or post-secondary education as part of a guideline child support order, though parents can agree to it.
- Earlier end: support ends if the child marries, joins the military, or becomes self-supporting.
- A disabled adult child: a court can order support to continue for a child who is incapable of self-support because of a disability.
Parents moving from a state with a higher age — or one that orders college contributions — are often surprised that California stops at 18 or 19.
Official California child support resources
Every link below goes to an official California source — the Department of Child Support Services, the official Guideline Calculator, or the Family Code itself. Bookmark the ones you’ll use.
| Resource | What it’s for | Official link |
|---|---|---|
| California Child Support Services (DCSS) | Open a case, find your local agency | childsupport.ca.gov |
| Official Guideline Calculator | Estimate your payment | California Guideline Calculator |
| Customer Connect | View your case and payment history | Customer Connect |
| Payer Dashboard | Make and manage payments | Payer dashboard |
| Family Code § 4055 | The statewide guideline formula | leginfo.legislature.ca.gov |
| Family Code § 4059 | What net disposable income includes | leginfo.legislature.ca.gov |
| Family Code § 3901 | When support ends (age 18/19) | leginfo.legislature.ca.gov |
| SB 343 (2023–2024) | The 2024 guideline overhaul | leginfo.legislature.ca.gov |
| Phone — Child Support | Statewide help line | 1-866-901-3212 |
Comparing states? See our guides to child support in Colorado and child support in Indiana, which use income-shares schedules, and child support in Texas, which uses a flat percentage of the paying parent’s income — three very different approaches to the same question. For how every state’s rules compare, see our child support by state overview.
Frequently Asked Questions
How is child support calculated in California?
California uses a statewide guideline formula, CS = K(HN − H% × TN), set out in Family Code § 4055. It runs on both parents’ net monthly disposable incomes and the higher earner’s share of parenting time, with a K-factor that shifts across income bands. Because the math is complex, the state and courts rely on certified software, and parents should use the official California Guideline Calculator rather than estimating by hand.
How much is child support for one child in California?
There’s no flat amount or percentage — it depends on both parents’ net incomes, the parenting-time split, tax and health-premium deductions, and any add-ons. A large income gap with little parenting time for the higher earner produces a high number; similar incomes with a near-equal schedule produce a low one. The only reliable figure comes from running your actual numbers through the official Guideline Calculator.
Did California child support change in 2024?
Yes. Senate Bill 343 became operative September 1, 2024. It updated the formula’s K-factor brackets for the first time since 1992, raised the low-income adjustment threshold to roughly full-time minimum-wage earnings, and changed the default for add-on costs like childcare and uninsured medical from a 50/50 split to each parent’s share of income. The changes apply to orders set or modified on or after that date.
Do you still pay child support with 50/50 custody in California?
Often, but less. California builds parenting time directly into the formula as the higher earner’s timeshare percentage, so an equal split lowers the guideline amount. When both parents earn similar incomes and share time equally, support can be small or near zero. When one parent earns significantly more, that parent usually still pays something even with a 50/50 schedule, because the formula evens out the children’s standard of living between two homes.
At what age does child support end in California?
Usually 18. Under Family Code § 3901, support ends at 18, but it extends to 19 — or until the child completes 12th grade, whichever comes first — if the child is still a full-time high school student and not self-supporting. It can end earlier if the child marries, joins the military, or becomes self-supporting, and it can continue for an adult child who cannot support themselves because of a disability.
Does California child support cover college?
No. California does not require parents to pay for college or other post-secondary education as part of a guideline child support order. Support generally ends at 18 or 19. Parents are free to agree to share college costs in a written agreement, and a court can enforce that agreement, but it is not part of the standard child support obligation.
Is there an official California child support calculator?
Yes. The state offers the California Child Support Guideline Calculator, which uses the same legal guideline the courts apply, including the 2024 SB 343 changes. You enter both parents’ income, tax filing status, parenting-time percentage, health-insurance and childcare costs, and it estimates the guideline amount. Treat the result as an estimate — the court makes the final decision and can deviate for good cause.
What happens if you don’t pay child support in California?
The state can withhold wages, suspend driver’s and professional licenses, intercept tax refunds and lottery winnings, levy bank accounts, place liens, report the debt to credit bureaus, deny a passport once arrears reach $2,500, and pursue contempt that can carry jail time. Unpaid support also accrues interest at 10% per year and can’t be discharged in bankruptcy, so request a modification if you can’t keep up rather than letting a balance build.
Note: This article is general information, not legal advice. Child support laws and amounts change, and individual cases vary. For decisions about your specific situation, consult a family-law attorney licensed in California.
