California Family Code 4323 creates a rebuttable presumption that a supported spouse needs less spousal support once they begin cohabiting with a nonmarital romantic partner. It does not end support automatically. It shifts the burden: instead of the paying spouse proving the recipient needs less money, the recipient has to prove they still need the same amount. The court can then reduce support, terminate it, or leave it alone.
What the Presumption Actually Does
The mechanism is a burden shift, not a rule of outcome.1California Legislative Information. California Family Code 4323 In an ordinary spousal support modification, the person asking for the change carries the full weight of showing why it is justified. Under Section 4323, once the paying spouse establishes cohabitation, the law presumes the supported spouse’s financial need has dropped. The supported spouse then has to come forward with evidence to keep support where it is.
That’s a harder argument to make from inside a shared household than from outside one. Courts recognize two reasons cohabitation typically reduces need: sharing a home creates economies of scale on rent, utilities, and groceries, and the new partner’s income may become partially available to the supported spouse.2Justia Law. In re Marriage of Bower Either can justify a reduction even when the new partner isn’t wealthy.
What Counts as Cohabitation
Cohabitation under Section 4323 means something more than sharing a roof. California courts have held that the word carries special legal significance and describes a marriage-like arrangement: shared daily life, romantic involvement, and some level of financial interdependence.2Justia Law. In re Marriage of Bower Two people renting rooms in the same house with separate finances and no romantic connection don’t qualify. Neither does casual dating without a shared residence, or a temporary stay with a friend or family member.
The statute is explicit that the couple does not need to hold themselves out as spouses.1California Legislative Information. California Family Code 4323 They don’t have to share a last name, file taxes jointly, or call themselves a couple. What matters is how they actually live.
The kinds of evidence that tend to carry weight:
- Joint bank accounts, shared bills, or one partner paying the other’s expenses
- A shared bedroom, joint lease, or joint ownership of the home
- An intimate or companion relationship, not a landlord-tenant one
- Shared meals, household responsibilities, vacations, and social life as a couple
When a Written Agreement Blocks the Presumption
Section 4323 opens with “except as otherwise agreed to by the parties in writing.”1California Legislative Information. California Family Code 4323 If your marital settlement agreement or stipulated judgment addresses cohabitation directly, that written language controls. Some settlements waive the presumption, fix support at a set amount regardless of living arrangements, or spell out their own modification triggers.
Family Code 3651 goes further: spousal support cannot be modified or terminated when a written agreement specifically states it is non-modifiable, and an oral agreement made in open court has the same effect.3California Legislative Information. California Family Code 3651 Before filing anything, read your judgment carefully. That is where most people either save themselves a wasted filing fee or spot a clause they’d forgotten about.
Filing Under Section 4323
The paying spouse files a Request for Order on form FL-300 with the superior court that issued the original support order.4California Courts | Self Help Guide. Request for Order FL-300 An Income and Expense Declaration on form FL-150 goes with it.5California Courts. Ask for Temporary Spousal Support The motion fee under the current statewide schedule is $60.6California Courts. Statewide Civil Fee Schedule Effective 01-01-2026
The FL-300 should identify cohabitation as the changed circumstance and, in the “Facts to Support” section, lay out when it began, who the new partner is, and what financial benefits flow to the supported spouse from the arrangement. After filing, the paying spouse must serve the papers on the other side. Without proper service the court will not move forward, and the date of service also matters for how far back a reduction can reach.5California Courts. Ask for Temporary Spousal Support
How the Supported Spouse Overcomes the Presumption
Once cohabitation is established, the burden is on the supported spouse to show the arrangement hasn’t actually cut their financial need. The strongest response is documentary: separate bank statements, individual lease or mortgage payments, separate utility accounts, and clear proof that each person pays their own way.
The argument isn’t impossible, just difficult. Someone living with an unemployed partner or a partner with minimal income may genuinely be receiving no material financial benefit. Beyond separate finances, the supported spouse can point to ongoing needs the cohabitation doesn’t touch, such as medical expenses, marital debt, or the cost of maintaining the marital standard of living. The court weighs the full picture before deciding whether the presumption has been rebutted.
Why the Filing Date Matters
A modification can be made retroactive, but only back to the date the motion was filed, not to the date cohabitation began. Every month a paying spouse waits after learning of the cohabitation is a month that cannot be recovered. If the court later reduces or terminates support retroactive to the filing date, the supported spouse can be ordered to repay the excess already collected, and the court has flexibility over how that repayment is structured.7California Legislative Information. California Family Code 3653 File promptly once the evidence is in hand.
The Paying Spouse’s New Partner Is Off Limits
Section 4323(b) runs in the opposite direction for the paying side. The income of the paying spouse’s new spouse or nonmarital partner cannot be considered when setting or modifying spousal support.1California Legislative Information. California Family Code 4323 A supported ex cannot argue that the payer’s remarriage or cohabitation increases the ability to pay. Support stays tied to the paying spouse’s own finances.
Possible Outcomes and Later Modifications
At a Section 4323 hearing the court can reduce support, terminate it, or leave it in place if the supported spouse rebuts the presumption. A reduction is the common middle result when there is some shared financial benefit but genuine remaining need. Termination is more likely when the new partner has effectively taken over the financial role the paying spouse once filled.
The decision isn’t permanent. Section 4323(c) preserves the right to seek further modifications later based on new changed circumstances.1California Legislative Information. California Family Code 4323 If support is reduced and the cohabitation later ends, the supported spouse can file again arguing renewed need. If a motion is denied because the presumption was rebutted, the paying spouse can come back when the financial dynamics of the household shift.