An infidelity clause in a New York prenup is legally permissible, but no appellate court in the state has ruled on whether one is enforceable. That silence means a judge handling your divorce could enforce the clause as written, strike it while keeping the rest of the agreement intact, or, in the worst case, void the whole contract as unconscionable. Which outcome you get depends almost entirely on how the clause is drafted, how the penalty is sized against your marital estate, and whether the agreement meets every technical requirement New York imposes on premarital contracts.
Where the Law Actually Stands
New York adopted no-fault divorce in 2010 through subdivision 7 of Domestic Relations Law § 170, letting a spouse end a marriage by swearing the relationship has been irretrievably broken for at least six months.1New York State Senate. New York Domestic Relations Law 170 – Action for Divorce A clause that forces a court to litigate who cheated runs against that current. Judges are cautious about contract terms that drag fault proceedings back into a system the Legislature deliberately moved away from.
At the same time, New York has strong public policy favoring the right of couples to settle their own financial affairs by contract. A properly executed prenup carries the same presumption of legality as any other contract, and setting one aside is “the exception rather than the rule.”2NY Courts. Gottlieb v Gottlieb, 2016 NY Slip Op 00613 The practical takeaway is that practitioners drafting infidelity clauses are working from general contract principles and unconscionability doctrine rather than any on-point ruling. A well-drafted clause may hold because nothing prohibits it; a sloppy one gives the judge wide latitude to walk away from it.
Define Cheating Precisely or the Clause Will Fail
Vague language is the single biggest threat to an infidelity clause. Writing “cheating” or “infidelity” without a definition hands the court a subjective interpretation problem that judges will not want to solve. The clause has to describe the triggering conduct specifically enough that both parties know exactly where the line sits.
Decide whether the clause covers physical sexual contact only, or stretches to emotional affairs and digital interactions. A provision limited to sexual intercourse is easier to prove and harder to dispute. Broader definitions covering active dating app profiles, sexting, or sustained romantic communication with a third party catch more conduct but open the door to litigation over whether specific behavior qualifies. Narrow and objective enforces better than wide and interpretive.
Then there is proof. Text messages, emails, social media records, and photographs are the usual evidence, and how they were obtained matters. A spouse who accessed the other’s phone or accounts without permission can run into federal wiretapping law and state privacy protections that make the evidence inadmissible. The agreement itself can address this directly by including a consent provision for reasonable monitoring, or by stating that only voluntarily disclosed or lawfully obtained evidence can trigger the penalty. Leaving the evidence question open invites a dispute over admissibility that can swallow the infidelity question entirely.
Choose a Penalty Structure That Will Survive Review
Once the conduct is defined, the agreement has to spell out exactly what the unfaithful spouse owes. There are three common approaches, and they can be combined.
Lump-Sum Payments
The simplest penalty is a fixed dollar amount paid by the unfaithful spouse to the other. A predetermined number avoids drawn-out valuation disputes. The amount has to be proportional to the overall marital estate. Several hundred thousand dollars might be reasonable for a couple with an eight-figure net worth and look unconscionable in a middle-class household. Proportionality is the factor most likely to decide whether the judge enforces the payment or sets it aside.
Shifting the Property Division
New York is an equitable distribution state, with marital property divided based on 16 statutory factors rather than any automatic split.3New York State Senate. New York Domestic Relations Law 236 – Special Controlling Provisions; Prior Actions or Proceedings; New Actions or Proceedings An infidelity clause can override that analysis by dictating a specific split, such as giving the faithful spouse 60 or 70 percent of the marital estate. The agreement should identify which assets are subject to the shift: real estate, investment accounts, retirement funds, or everything.
Maintenance Waivers
A clause can provide that the unfaithful spouse forfeits spousal maintenance, which can represent significant money because New York calculates post-divorce maintenance from a statutory formula tied to both parties’ incomes, subject to an income cap that adjusts every two years for inflation.3New York State Senate. New York Domestic Relations Law 236 – Special Controlling Provisions; Prior Actions or Proceedings; New Actions or Proceedings Maintenance waivers carry risks that other penalties do not. A waiver cannot stand if it would leave the forfeiting spouse unable to support themselves and likely to become a public charge, a limit imposed by General Obligations Law § 5-311.4Justia Law. J.M. v G.V., 2025 NY Slip Op 25004 A stay-at-home spouse who gave up a career during a long marriage is exactly the scenario where a court will refuse to enforce a total maintenance forfeiture, infidelity clause or not.
The Maintenance Waiver Trap from J.M. v. G.V.
Anyone drafting an infidelity-triggered maintenance forfeiture needs to know about the 2025 decision in J.M. v. G.V. The court vacated the maintenance waiver in a prenuptial agreement because the document failed to include both parties’ incomes at the time of signing and did not provide the full calculation of what the guideline maintenance amount would have been. Without those numbers, the court held, there could be no “knowing waiver” of the right to maintenance.4Justia Law. J.M. v G.V., 2025 NY Slip Op 25004
The requirement bites hardest when either spouse is not represented by an attorney. The statute requires the full maintenance guidelines calculation to be laid out explicitly so that a self-represented party understands the dollar value of what they are giving up.4Justia Law. J.M. v G.V., 2025 NY Slip Op 25004 A prenup that includes a maintenance forfeiture triggered by infidelity but skips the income figures and guideline calculation at signing can lose the entire maintenance provision regardless of whether anyone cheated. Many infidelity clauses fall apart here. Couples focus on the dramatic penalty language and overlook the technical compliance New York demands around maintenance.
The Unconscionability Line
If the clause is challenged, the fight will center on unconscionability. New York defines an unconscionable bargain as one “which no person in his or her senses and not under delusion would make on the one hand, and no honest and fair person would accept on the other, the inequality being so strong and manifest as to shock the conscience.”5Justia Law. E.K. v C.K., 2022 NY Slip Op 50811(U) That bar is high, but infidelity penalties can clear it in the wrong direction. An agreement that leaves one spouse financially devastated after a single affair is the textbook example.
Courts also treat agreements between spouses as involving a fiduciary relationship requiring the utmost good faith, a higher standard than ordinary business contracts.5Justia Law. E.K. v C.K., 2022 NY Slip Op 50811(U) A one-sided clause is not automatically unconscionable, but the distance between one-sided and unconscionable shrinks when the penalty punishes personal conduct rather than allocating property. Under § 236(B)(3), maintenance terms face a two-part test: they must be fair and reasonable when signed and cannot be unconscionable at the time of the final divorce judgment.3New York State Senate. New York Domestic Relations Law 236 – Special Controlling Provisions; Prior Actions or Proceedings; New Actions or Proceedings A clause that looked reasonable on your wedding day can still fail the second prong if circumstances changed enough over the marriage.
The spouse challenging the prenup bears the burden of proving fraud, duress, overreaching, or unconscionability, and a prenup that looks fair on its face gets enforced unless the challenger comes forward with particularized evidence of inequality.2NY Courts. Gottlieb v Gottlieb, 2016 NY Slip Op 00613 That protects a well-drafted clause but does not make it bulletproof. A penalty that is disproportionate to the marital estate gives the challenger exactly the ammunition the standard requires.
What the Clause Cannot Reach
No matter what the infidelity clause says, child custody and child support remain under the court’s independent authority. Section 236(B)(3) allows prenups to address “the custody, care, education and maintenance of any child,” but those provisions are always subject to the court’s determination of the child’s best interests under DRL § 240.3New York State Senate. New York Domestic Relations Law 236 – Special Controlling Provisions; Prior Actions or Proceedings; New Actions or Proceedings An infidelity clause cannot strip the other parent of custody or reduce child support. The judge will ignore any such provision and apply the statutory child support guidelines independently.
Infidelity can occasionally surface in custody proceedings on its own, if a parent’s conduct created a living situation that harmed the child or demonstrated poor judgment affecting the child’s welfare. The prenup itself plays no role in that analysis. Linking cheating to custody changes in the agreement is wasted ink.
Execution Steps That Give the Clause a Fighting Chance
Sign the prenup well before the wedding. An agreement presented the week before the ceremony invites the argument that one spouse signed under pressure with no real ability to negotiate. The further in advance you execute the document, the harder it is for either party to later claim coercion.
Each spouse should have independent counsel. It is not statutorily required, but the absence of separate lawyers is the most common basis for setting a New York prenup aside. Having your own attorney review the infidelity clause, the financial provisions, and the maintenance figures shows that both parties entered the agreement with full understanding. If one spouse cannot afford counsel, the other paying for that representation is a reasonable cost to protect the agreement.
Full financial disclosure is not legally required in New York, but exchanging it voluntarily makes the agreement much harder to challenge. Attach schedules showing each party’s income, assets, and debts. For any maintenance provision, including the full guidelines calculation with current income figures is what J.M. v. G.V. demands.
The signatures must be acknowledged in the manner required for recording a deed, which in practice means notarization.3New York State Senate. New York Domestic Relations Law 236 – Special Controlling Provisions; Prior Actions or Proceedings; New Actions or Proceedings A botched or missing acknowledgment is a fatal defect no infidelity drafting can rescue.
Build in a severability provision. With no appellate guidance on infidelity clauses, there is a real possibility a judge strikes the infidelity penalty while leaving the rest of the prenup standing. Without severability, the court could void the entire agreement if it finds the lifestyle clause unenforceable. Severability protects the property division, maintenance terms, and everything else you negotiated even if the infidelity provision does not survive.