The California alimony formula everybody quotes is one county’s local rule.
There is no statewide spousal support formula. The arithmetic is county law, it applies only while the case is running, and it stops at the courthouse door on the day of judgment.
California has no statewide spousal support formula. Not in the Family Code, and not in the California Rules of Court. The number everybody quotes — 40 per cent of the payor’s net income minus 50 per cent of the payee’s — is a county local rule, and it governs temporary support only.
The proof is that the next county over uses a different one. Both are quoted below, from the counties’ own published rules.
And California calls it spousal support, not alimony. Part 3 of Division 9 of the Family Code is captioned “SPOUSAL SUPPORT”. The parallel term for registered domestic partners is partner support, which is the phrase the county rules use. The Family Code sections we read do not use the word “alimony” at all.
OneTwo counties, two different formulas
If it were state law it would be the same in both. It is not.
Local Family Rules, Rule 3.C
“Temporary spousal or partner support is generally computed by taking 40% of the net income of the payor, minus 50% of the net income of the payee, adjusted for tax consequences. If there is child support, temporary spousal or partner support is calculated on net income not allocated to child support and/or child-related expenses.”
Local Rules, Rule 5.70
“The following discretionary guideline is adopted… (a) Non-child support cases… 40% of the net income of the payor or minus 50% of the net income of the payee. (b) Child support cases… uses the components set forth in Family Code sections 4055 through 4069 in the following formula: SS = [HN-(HN)(M)(K)(1+H%)][.35] – [LN-(LN)(M)(K)(1+H%)][.4]”
Sources: santaclara.courts.ca.gov and alameda.courts.ca.gov. Both re-checked 23 August 2026 and both resolve.
What actually follows from this
Your county’s rule is the one that applies to you, and the county next door may run a different calculation on the same two incomes. A calculator on a national website does not know which county you are in, and most of them are quietly running Santa Clara’s.
And Alameda calls its own version a discretionary guideline. Even inside the county, it is not binding arithmetic.
TwoIt stops on the day of judgment
This is the part that costs people money, because the temporary number is the one they have been living with for a year or more and they assume it carries forward.
It does not. The county guidelines govern temporary support while the case is running. The award made at the end of the case is governed by Cal. Fam. Code s. 4330, read through the circumstances in s. 4320 — and s. 4320 contains no arithmetic at all.
Cal. Fam. Code s. 4330(a), verbatim: “In a judgment of dissolution of marriage or legal separation of the parties, the court may order a party to pay for the support of the other party an amount, for a period of time, that the court determines is just and reasonable, based on the standard of living established during the marriage, taking into consideration the circumstances as provided in Chapter 2 (commencing with Section 4320).”
Section 4320 then lists fourteen lettered circumstances, (a) through (n), which the court shall consider. They are set out in full on the main California alimony page. Not one of them is a percentage.
ThreeThe ten-year rule is not what it is usually said to be
A ten-year California marriage does not mean support for life
The ten-year rule lives in s. 4336, and it is a rule about how long the court keeps the power to act — not about how long money is paid.
Section 4336(b) creates “a presumption affecting the burden of producing evidence that a marriage of 10 years or more, from the date of marriage to the date of separation, is a marriage of long duration”, and the effect under (a) is that the court retains jurisdiction indefinitely. Then s. 4336(c), verbatim: “Nothing in this section limits the court’s discretion to terminate spousal support in later proceedings on a showing of changed circumstances.”
A page that says a ten-year California marriage means support for life is describing something the statute does not say.
Two more things sit alongside it. Section 4335: “An order for spousal support terminates at the end of the period provided in the order and shall not be extended unless the court retains jurisdiction in the order or under Section 4336.” And inside the factor list, s. 4320(l) states the goal that the supported party be self-supporting “within a reasonable period of time”, which “generally shall be one-half the length of the marriage” — followed immediately by a sentence disclaiming any limit on the court’s discretion. That is a goal with a disclaimer attached, not a bracket.
FourThe California tax change that took effect this year
If you read one section of this page, read this one. It is recent, it is specific to California, and almost nothing online has caught up with it.
Everyone knows the federal rule: for an instrument executed after 31 December 2018, alimony is not deductible by the payer and not taxable to the recipient, under the Tax Cuts and Jobs Act.
California did not follow. For instruments executed 1 January 2019 through 31 December 2025, the payer deducts and the recipient includes on the California return, via a Schedule CA adjustment. The Franchise Tax Board says it in terms: “We do not conform to the federal Alimony changes effective January 1, 2019, through December 31, 2025.”
That ended on 1 January 2026
Under SB 711, California conforms for any instrument executed on or after 1 January 2026 — and for an earlier instrument modified after that date where the modification expressly says the amendments apply.
Two orders signed either side of 1 January 2026 have different California treatment for their whole life. Not for a year. For the life of the order.
Why this is not a footnote. Support that is invisible on the federal return still moved money on the California one for every instrument signed between 2019 and the end of 2025. A settlement modeled on the federal treatment alone was mispriced in California — and if you are modifying such an order now, whether the modification adopts the new rule is a term worth real money to somebody.
California is one of only four states where the federal answer is not the whole answer. The others are Arkansas, New Jersey and New York — and no two of them got there the same way. New Jersey was never coupled to the federal rule at all; its Gross Income Tax Act defines income through its own closed list. Arkansas froze the federal rule in place. We set out all four, with each state’s own source, at which states still tax alimony. Everywhere else, the federal rule is the end of it.
Sources: Cal. Franchise Tax Board, “Alimony” (personal income types); Cal. Rev. & Tax. Code s. 17024.5(a)(1), the IRC conformity date table; SB 711 (2025–2026 session). Federal authority: Tax Cuts and Jobs Act, Pub. L. 115-97, s. 11051, repealing Internal Revenue Code sections 71 and 215; see also IRS Publication 504.
FiveConduct, and the three places it actually reaches
California is a no-fault state, and s. 4320 contains no general conduct or fault factor. Conduct reaches spousal support only through named channels, and all of them are tied to violence or a conviction.
| Section | What it does |
|---|---|
| s. 4320(i) | Directs the court to weigh “all documented evidence of any history of domestic violence, as defined in Section 6211”, with five enumerated kinds of evidence. |
| s. 4324 | An absolute bar. On conviction of attempting to murder, or soliciting the murder of, the other spouse, the injured spouse “shall be entitled to a prohibition of any temporary or permanent award for spousal support” and of insurance benefits. |
| s. 4324.5 | A flat bar. On a conviction for a violent sexual felony or a domestic violence felony against the other spouse, where the petition is filed within five years of conviction and time served, “an award of spousal support to the convicted spouse from the injured spouse is prohibited.” |
| s. 4325 | A rebuttable presumption to the same effect on a domestic violence misdemeanor conviction within the stated window. |
Both s. 4324.5 and s. 4325 allow the convicted spouse’s own history as a victim to be weighed against the bar or the presumption. Nothing in the Family Code makes adultery, desertion or cruelty relevant to spousal support.
And one more mandatory rule that has no discretion in it. Section 4322: “In an original or modification proceeding, where there are no children, and a party has or acquires a separate estate, including income from employment, sufficient for the party’s proper support, no support shall be ordered or continued against the other party.”
SixEnding it, changing it, and one thing the statute does not say
What ends it
Cal. Fam. Code s. 4337, verbatim and in full: “Except as otherwise agreed by the parties in writing, the obligation of a party under an order for the support of the other party terminates upon the death of either party or the remarriage of the other party.”
Cohabitation does not terminate support in California. It shifts a burden. Section 4323(a)(1) creates “a rebuttable presumption, affecting the burden of proof, of decreased need for spousal support if the supported party is cohabiting with a nonmarital partner”, and holding oneself out as a spouse is expressly not required. The same section closes off the argument in the other direction — s. 4323(b), in full: “The income of a supporting spouse’s subsequent spouse or nonmarital partner shall not be considered when determining or modifying spousal support.” There is no statutory retirement trigger.
The familiar rule that is not in the statute
“Material change of circumstances” does not appear in s. 3651
Everyone says California spousal support can only be modified on a material change of circumstances. The statutory text says something else. Section 3651(a): a support order “may be modified or terminated at any time as the court determines to be necessary”.
The changed-circumstances requirement is judicial gloss. The only places the Family Code itself uses that language for spousal support are s. 4323(a)(1), on cohabitation, and s. 4336(c), on terminating after a long marriage. We quote no California opinion here because we have not read one from a primary source — so this page tells you what the statute says and stops there.
Two limits that are in the statute and are worth knowing. Section 3651(c)(1): an order may not be modified “as to an amount that accrued before the date of the filing of the notice of motion or order to show cause” — so the filing date is the date that matters, and waiting costs money that cannot be recovered. And s. 3651(d): an order for spousal support may not be modified or terminated to the extent a written agreement, or an oral agreement entered in open court, specifically provides that it is not subject to modification. The same rule for support agreements is at s. 3591.
Where all of this comes from
Cal. Fam. Code s. 4330 (the award); s. 4320 (the fourteen circumstances); s. 4322 (mandatory denial where a separate estate suffices and there are no children); ss. 4324, 4324.5 and 4325 (conviction-based bars and presumptions); s. 4323 (cohabitation); s. 4335 (expiry of the term); s. 4336 (retained jurisdiction, marriage of long duration); s. 4337 (termination on death or remarriage); ss. 3651 and 3591 (modification). Section 4320 as printed carries the enactment line “Amended by Stats. 2018, Ch. 938, Sec. 1. (AB 929) Effective January 1, 2019.” leginfo.legislature.ca.gov
The county rules are quoted from the counties’ own published PDFs, linked above, both re-checked on 23 August 2026.
Every quotation on this page was read from an official source and is reproduced verbatim. Checked 23 August 2026. If a figure here has changed, or we have it wrong, tell us — corrections are published with the date and how long the error was live.
The rest of the California picture. All fourteen circumstances in s. 4320, quoted complete with no elision, are at alimony in California. The number that usually moves a budget more is child support. What it costs to file is at what a California divorce costs, and the forms and deadlines are in the California divorce kit.
Free, no account, nothing to sign up for. If somebody you know is working from a number a calculator gave them, section one is the part to send.
The Cusp is not a law firm and does not provide legal, financial, or tax advice. This page quotes California statutes, county court rules and the Franchise Tax Board and summarizes what they say; it is not advice about any particular case, and whether a given rule applies to you depends on facts this page cannot know. How this site makes money is published in full.