Can a Prenup Have a Cheating Clause?

Can you put a cheating clause in a prenup?

Nothing stops you from putting the words on the page. Couples do it, lawyers draft it, and the clause sits in the agreement looking like every other provision.

The problem arrives years later, in a courtroom, when someone asks a judge to apply it. At that point the clause faces two independent hurdles. If it fails either one, it does nothing.

• Lock one, permission. Is a financial penalty for infidelity a term this state will enforce at all?
• Lock two, proof. If it is, will this state let you put evidence of the affair in front of the court?

California closes both. Several other states close the first. And a clause that fails is not always harmless: in a badly drafted agreement it can give the other side an argument about the document as a whole.

What a cheating clause says

A cheating clause, also called an infidelity or conduct clause, has two halves. The first defines the triggering behavior. The second attaches a financial consequence.

The consequence half is easy to draft. It is usually one of:

• A fixed payment from the unfaithful spouse to the other.
• An increase in spousal support, or the loss of a support waiver the agreement otherwise contains.
• An unequal division of the marital estate, tilted toward the spouse who was cheated on.

The definition half is where these clauses come apart. "Infidelity" has to be pinned down tightly enough that a judge can apply it to facts. Does an emotional affair count? A dating profile? A single encounter during a separation the couple never formalized? Vague triggers give a court a reason to decline, and precise triggers push the couple into writing down, before the wedding, exactly which acts will cost money. That conversation tends to end the idea on its own.

For the wider family of behavior provisions, including weight and social-media terms, see how lifestyle and conduct clauses hold up. This page stays on infidelity.

Lock one: will a court allow the clause?

Prenups can cover far more than property, but not without limit. California is representative. Under Family Code section 1612(a), parties may contract about "any other matter, including their personal rights and obligations, not in violation of public policy or a statute imposing a criminal penalty."

That closing phrase is the whole fight. A penalty for cheating is a personal-conduct term, so it lives or dies on whether it violates public policy. And the public policy it runs into is no-fault divorce.

California grants dissolution on two grounds only: irreconcilable differences, or permanent legal incapacity to make decisions. Neither asks who was at fault. A clause that assigns a dollar figure to marital misconduct asks the court to do the one thing the divorce statute was written to stop doing.

The American Bar Association notes that every state now offers a no-fault path, though many keep fault grounds available alongside it. Where a state retains fault grounds, the tension is weaker and the analysis is less settled. Where the no-fault policy is strong, the California reasoning travels well. Your state governs, so treat the specifics below as California law rather than a national rule, and check the state-by-state guide for how your own rules differ.

Lock two: could you even prove it?

Suppose a clause clears lock one. You still have to show the court that the affair happened, and that is where the second lock closes.

Under California Family Code section 2335, "evidence of specific acts of misconduct is improper and inadmissible" in a pleading or proceeding for dissolution or legal separation, including depositions and discovery. The bar covers the discovery process, not only the hearing, so there is no earlier stage at which the material comes in.

Read that against the clause you drafted. The provision turns on proof of a specific act of misconduct. The statute says that proof is inadmissible. Photographs, messages, a confession, a private investigator's file: none of it has a route into the record. The clause can be sitting in a signed agreement, describing conduct that indisputably occurred, and still have nothing to operate on.

This is the part most write-ups skip, and it changes the decision. A reader who learns only that infidelity clauses are "hard to enforce" may conclude that careful drafting fixes it. Careful drafting does not open an evidentiary door that the legislature closed.

What California settled

California did not leave this to inference. In Diosdado v. Diosdado (2002) 97 Cal.App.4th 470, a couple signed an agreement, after the husband's affair, providing that a spouse who was sexually unfaithful would owe the other $50,000 in liquidated damages. When the marriage ended, the wife tried to collect.

The Court of Appeal held the provision unenforceable. Its reasoning was the one above: a financial penalty for infidelity conflicts with the public policy behind California's no-fault divorce law, because it reintroduces fault and marital blame into a proceeding the legislature deliberately made fault-blind. The court declined to put a price on the emotional injury of a broken promise of fidelity.

Diosdado remains the reference point for these clauses in California. It also explains why the answer does not turn on how much money is at stake or how sympathetic the facts are. The objection is structural.

Where infidelity can still change the outcome

Here is the part worth knowing before you give up on the idea entirely. In many states, marital fault already carries financial weight, through the state's own statutes rather than through anything you write into a prenup. The American Bar Association notes that many states permit fault grounds such as adultery, and that many weigh marital fault when awarding spousal support or dividing marital property.

Where that is true, a spouse who wants infidelity to matter financially may already have a route, and it is a route that does not put the prenup at risk. It is worth asking an attorney licensed in your state which of these applies to you:

• Whether your state still recognizes adultery as a ground for divorce, and what filing on it would involve.
• Whether marital misconduct is a statutory factor in setting spousal support where you live.
• Whether dissipation of marital assets applies. Money a spouse spent on an affair is often recoverable as dissipation, which is an economic claim about marital funds rather than a moral claim about conduct, and it survives in places where a conduct clause would not.

That last one does more work than most people expect, and it is available without drafting anything unusual into the agreement.

What to do instead

If the underlying worry is financial rather than moral, the prenup can address it directly, using terms that hold up:

1. Protect the assets you care about. Separate property, a business, an inheritance, and pre-marital savings can all be walled off by ordinary provisions that no court objects to. See what you can and cannot include in your prenup.
2. Address dissipation head on. A clause about how marital funds may be spent, or a requirement to account for large withdrawals, is an economic term rather than a conduct penalty.
3. Set the support terms deliberately. Deciding spousal support in advance is a normal use of a prenup, and it is where the financial consequence a reader wants often belongs.
4. Keep the agreement severable. If you include an unusual term against advice, a well-drafted severability provision limits the damage when a court strikes it. That is drafting hygiene, not a fix.
5. Get independent counsel on both sides. A clause that could jeopardize the surrounding agreement is exactly the situation where each partner needs their own attorney reviewing it.

An unusual clause also raises the stakes on the rest of the document, because a challenge to one provision is often an opening to attack the whole. On what makes the surrounding agreement survivable, see what makes a prenup enforceable.

Frequently Asked Questions

Can I add an infidelity clause to my prenuptial agreement?

You can write one in. Whether it does anything depends on your state, and in California it does not. California enforces prenups but declines infidelity penalties, because they conflict with the public policy behind no-fault divorce. Ask an attorney licensed in the state whose law will govern your agreement before including one.

Are infidelity clauses in prenups enforceable?

Often not. State law lets couples contract about personal rights and obligations only where the terms do not violate public policy, and a financial penalty for cheating reintroduces fault into a system built to be fault-blind. In California the question is settled by Diosdado v. Diosdado (2002) 97 Cal.App.4th 470, which held a $50,000 infidelity penalty unenforceable.

Does cheating void a prenup?

No. Infidelity does not invalidate an otherwise valid prenuptial agreement. Prenups are set aside for defects in how they were made, such as hidden assets, coercion, unconscionable terms, or missing formalities, and not for what a spouse did during the marriage. If your agreement has no infidelity clause, cheating generally has no effect on how it is applied.

What does an infidelity clause look like?

It defines the triggering conduct, then attaches a consequence: a fixed payment, an increase in spousal support, or an unequal division of the marital estate. The definitional half is where these clauses fail. "Infidelity" has to be precise enough for a court to apply, and precision means agreeing in advance on exactly which acts trigger the penalty.

Can you put a cheating clause in a prenup in California?

You can write one, and it will not be enforced. Diosdado settled the public-policy question, and Family Code section 2335 independently makes evidence of specific acts of misconduct inadmissible in a dissolution proceeding, so there is no way to prove the trigger even if the clause survived. See our California prenup guide.

Does a cheating clause put the rest of my prenup at risk?

It can. An unenforceable term gives the other side something to attack, and a challenge aimed at one provision often becomes a challenge to the agreement as a whole. A severability clause limits the exposure but does not remove it, which is why most family law attorneys advise against including a conduct penalty at all.

If you are weighing a clause

The couples who raise this are usually trying to solve something real: a past betrayal, a gap in earnings, an asset one partner is anxious about. Those concerns can be written into a prenup in terms that hold. A conduct penalty is one of the few that cannot.

Deciding which of those applies to you is a judgment call about your state and your finances, and it is the kind of call each partner should be getting from their own lawyer rather than from the other partner. First's Lawyer Review package gives each partner an independent family law attorney inside one flat fee, which is the structure this particular question calls for.

Methodology

The statutory analysis here is California law, quoted from the Family Code sections linked below, and is used because California has the clearest rule on infidelity clauses and a published appellate decision applying it. The two-lock framework generalizes; the specific thresholds do not. States that retain fault grounds treat these clauses less uniformly. Where this page describes national conditions it relies on the American Bar Association rather than extrapolating from California, and no state is described as enforcing an infidelity clause, because we could not verify one that does.

Sources

• California Family Code section 1612: subsection (a) permits terms on personal rights and obligations only where they do not violate public policy or a statute imposing a criminal penalty.
• California Family Code section 2310: the grounds for dissolution are irreconcilable differences or permanent legal incapacity to make decisions.
• California Family Code section 2335: evidence of specific acts of misconduct is improper and inadmissible in a dissolution or legal separation proceeding, including in depositions and discovery.
• Diosdado v. Diosdado (2002) 97 Cal.App.4th 470 (Cal. Ct. App.): a liquidated-damages provision penalizing sexual infidelity held unenforceable as contrary to the public policy of California's no-fault divorce law.
• American Bar Association, Divorce: all states offer a no-fault path; many retain fault grounds such as adultery, and many weigh marital fault in awarding spousal support or dividing marital property.

First is not a law firm. The information and tools provided by First on this site are not legal advice and not a substitute for the advice of an attorney.