California changed how child support is calculated. If your information is from before September 2024, your number may be wrong. A major overhaul updated the formula for the first time in decades.
This guide explains how child support is calculated in California, what the new law changed, and why an existing support order may be worth a second look.
The California child support formula
California uses a statewide guideline formula to calculate child support. The formula is designed to produce a consistent, presumptively correct amount based on the parents’ finances and parenting time.
At a high level, the guideline looks at each parent’s net disposable income and the percentage of time each parent spends caring for the children. A parent who earns more, or who spends less time with the children, generally pays more support.
The calculation runs through guideline software that courts and attorneys use. While the inputs can get detailed, the core idea is simple: child support reflects both parents’ ability to provide and the share of time each parent has the children.
What goes into the calculation
Two main inputs drive the guideline amount: income and time.
Net disposable income is each parent’s income after certain allowable deductions, such as taxes, mandatory retirement contributions, and health insurance premiums. The court starts with gross income from nearly all sources and then subtracts those items.
Parenting time, often called timeshare, is the percentage of time each parent is responsible for the children. The more time a parent has, the more that parent is presumed to spend directly on the children, which affects the support figure.
Because both income and parenting time matter, a change in either one can change the support amount. A new job, a raise, or a revised custody schedule can all be reasons to recalculate.
What SB 343 changed in 2024
Senate Bill 343 took effect on September 1, 2024, and it modernized a formula that had not been meaningfully updated in more than thirty years.
The law revised the guideline’s underlying math, often described as the K-factor, which determines how much of the parents’ combined income goes toward support. The income bands were recalibrated so the formula better reflects today’s wages and cost of living.
The changes adjust how support is figured for lower-income parents while recalibrating contributions across income levels. The goal was a formula that more accurately mirrors what families actually earn and spend now, rather than economic conditions from decades ago.
Another technical change involved how certain thresholds are set. The law moved away from using the Consumer Price Index for the low-income adjustment and tied that threshold to the state minimum wage instead.
The low-income adjustment
One of the most important parts of SB 343 is how it treats lower-earning parents through the low-income adjustment.
The adjustment is meant to keep child support realistic for parents with limited means, so an order does not push a low-earning parent below a basic standard of living. After SB 343, the threshold is based on full-time earnings at the California minimum wage.
As of January 1, 2026, the low-income adjustment generally applies to parents earning up to approximately 2,929 dollars per month. That figure reflects full-time work at the current state minimum wage of 16.90 dollars per hour, and it can rise as the minimum wage rises.
For parents near that threshold, the adjustment can meaningfully reduce the guideline amount, so it is an important part of any accurate calculation.
Add-on expenses beyond the base amount
The guideline figure is not always the whole story. California law also requires parents to share certain additional costs, known as add-ons, on top of base support.
Mandatory add-ons include childcare costs that allow a parent to work or get training, and the children’s uninsured health care expenses. These are typically divided between the parents.
Under the updated rules, add-on expenses are generally split in proportion to each parent’s net income rather than automatically being divided down the middle. A parent who earns more of the combined income usually pays a larger share of these costs.
Discretionary add-ons, such as private school tuition or expenses for a child’s special needs, can also be ordered when appropriate. Our overview of child support in California covers how these pieces fit together. Contact an Orange County child support lawyer to help.
Why your existing order may need a second look
Because SB 343 changed the math, an order calculated under the old formula may not match what the guideline would produce today.
That does not mean every order automatically changes. But if your order predates September 2024, or if your income or parenting time has shifted, it is worth running the numbers under the current rules.
Either parent can ask the court to modify support when there has been a significant change in circumstances, or when an existing order no longer matches the guideline. A recalculation can move the number up or down depending on the details.
You can estimate a starting figure using our California child support calculator, then confirm the specifics with an attorney.
Common child support myths
Several misunderstandings lead parents astray.
One common myth is that equal, fifty-fifty custody means no one pays child support. That is not true. Even with equal parenting time, a difference in the parents’ incomes usually still results in a support obligation, because support reflects income as well as time.
Another myth is that child support and parenting time are a trade, so withholding one justifies withholding the other. They are separate legal duties. A parent cannot stop paying support because of a visitation dispute, and a parent cannot deny visitation because support is unpaid. Learn more about how custody and parenting time are decided.
How tax treatment affects child support
Unlike spousal support, child support is not tax deductible for the paying parent and is not taxable income for the receiving parent. It is treated as a transfer for the children’s benefit, not as income.
That said, related issues, such as which parent claims the children as dependents, can have tax consequences and are often addressed as part of the overall agreement. Coordinating these details helps avoid surprises at tax time.
An example of how the formula works
A simple example helps show how the pieces fit together. Imagine two parents where one earns noticeably more than the other and the children spend most nights with the lower earner.
The guideline software takes each parent’s net disposable income and the percentage of parenting time and produces a base support figure. Because the higher earner has both more income and less parenting time, that parent typically pays support to the other.
Change one input and the result moves. If the higher earner takes on more overnights, the support amount usually drops. If that parent’s income rises, the amount usually increases. This is why precise, current numbers matter so much.
Determining income for self-employed parents
Income is straightforward for a salaried employee, but it gets complicated when a parent is self-employed or has variable earnings.
For business owners, the court looks at income after legitimate business expenses, and it can scrutinize deductions that look more like personal spending. Bonuses, commissions, and seasonal work may be averaged over time to find a fair monthly figure.
When a parent is intentionally unemployed or underemployed, the court can base support on earning capacity rather than actual earnings. In other words, a parent cannot avoid support simply by choosing to earn less than they are able to.
How long child support lasts
In California, child support generally continues until a child turns 18, or until 19 if the child is still a full-time high school student and not self-supporting.
Support can extend longer in limited situations, such as for a child who is unable to support themselves due to a disability. Parents can also agree to continue support for expenses like college, though courts generally do not order that on their own.
Support does not end automatically the moment a child reaches the age cutoff if there are arrears or multiple children covered by one order. It is important to confirm when an obligation actually terminates.
Enforcing a child support order
A child support order is a court order, and there are real tools to enforce it when a parent does not pay.
Enforcement options include wage garnishment, intercepting tax refunds, placing liens, and suspending licenses. Unpaid support, known as arrears, accrues interest and does not simply disappear over time.
If you are owed support or are struggling to pay, the right move is to address it through the court rather than letting the problem grow. A modification, where appropriate, is far better than falling into arrears.
Can parents agree on their own amount?
Parents can agree to a child support amount, but there is an important limit. They cannot agree to less than the guideline amount unless the court is satisfied the children’s needs are met and the agreement is truly in the children’s interest.
The guideline amount is considered presumptively correct, and a judge must approve any departure from it. Parents are free to agree to more than the guideline figure, and many do to cover extras like activities or education. Putting the agreement in writing and having the court enter it as an order is what makes it enforceable.
Frequently asked questions
How is child support calculated in California?
California uses a statewide guideline formula based on each parent’s net disposable income and the percentage of parenting time each parent has, run through guideline software to produce a presumptively correct amount.
What did SB 343 change?
Effective September 1, 2024, SB 343 updated the guideline formula and income bands for the first time in over thirty years, adjusted the low-income threshold to track the minimum wage, and changed how add-on expenses are shared.
Does 50/50 custody mean no child support?
No. Even with equal parenting time, a difference in the parents’ incomes typically still results in a support payment, because the formula considers income as well as time.
Can I change an existing child support order?
Yes. Either parent can request a modification when there is a significant change in circumstances, such as a change in income or parenting time, or when the order no longer reflects the current guideline.
Talk with an Orange County child support attorney
The 2024 changes make it more important than ever to calculate child support correctly. To understand what the current formula means for your family, contact our team to discuss your situation.
This article is provided for general educational purposes only and is not legal advice. It is not tax advice. Laws change and every situation is unique. For guidance about your specific circumstances, please consult a licensed California family law attorney.
