Postnuptial Agreement in New York: What It Covers and How to Get One

A prenuptial agreement is signed before the wedding. A postnuptial agreement does the same job — defining how assets, debts, and maintenance will be handled if the marriage ends — but is executed after the couple is already married. In New York, postnuptial agreements are enforceable, but courts scrutinize them more closely than prenups because of the fiduciary duty spouses owe each other during marriage.

If you missed the prenup window or your financial circumstances have changed significantly since the wedding — a business launched, an inheritance received, a career shift — a postnup may be the most practical way to protect assets that would otherwise be subject to equitable distribution.

What a Postnuptial Agreement Can Do

A postnup can address the same financial issues that a prenup covers:

• Classify specific assets as separate property — keeping an inheritance, business interest, or investment account off the equitable distribution table if the marriage ends
• Set spousal maintenance terms — agreeing in advance on the amount, duration, or waiver of maintenance rather than leaving it to the statutory formula
• Allocate responsibility for specific debts — assigning student loans, business debts, or credit card balances to the spouse who incurred them
• Define what happens to the marital home — specifying a buyout formula, sale trigger, or occupancy arrangement
• Protect a family business — preventing the business from being valued and divided as a marital asset, or establishing a predetermined valuation method

A postnup cannot waive child support or dictate child custody arrangements. Courts in New York retain full authority over child-related issues regardless of what the parties agree to privately.

What New York Courts Require for Enforcement

New York treats postnuptial agreements as contracts, governed by DRL § 236(B)(3). To be enforceable, a postnup must satisfy strict formal requirements:

Written and signed. Oral postnuptial agreements are unenforceable. The agreement must be in writing, signed by both parties, and acknowledged before a notary public in the same manner as a deed.

Full financial disclosure. Each spouse must provide complete and accurate disclosure of their assets, income, and liabilities. A spouse who later discovers that the other concealed a significant asset can challenge the entire agreement on grounds of fraud.

No duress or overreaching. Courts examine the circumstances surrounding execution more carefully than with prenups. Because spouses owe each other a fiduciary duty during marriage, a postnup signed under pressure — during an argument, as a condition for staying in the marriage, or without adequate time to review — is vulnerable to challenge.

Independent legal counsel. While not strictly required, courts strongly favor postnups where each spouse had their own attorney. An agreement where one spouse drafted the document and the other signed without independent review raises an inference of overreaching that can defeat enforcement.

Substantive fairness. Unlike prenups, which are generally enforced as long as the procedural safeguards were followed, postnups face a fairness review. A court may refuse to enforce terms that are unconscionable — grossly one-sided to the point that no reasonable person would agree to them absent coercion or misinformation.

Postnup vs. Prenup: Key Differences

The major difference is the fiduciary duty. Before marriage, the parties deal at arm's length — each looks out for their own interests. Once married, New York law imposes a fiduciary relationship, meaning each spouse has a duty of good faith, fair dealing, and full transparency toward the other.

This higher standard of duty means:

• Courts require more thorough financial disclosure for postnups than prenups
• The burden of proof shifts — the spouse seeking to enforce the postnup may need to demonstrate it was fair at the time of execution
• The "unconscionability" defense (arguing the terms are grossly unfair) is more likely to succeed against a postnup than a prenup

Practically, this means postnups need to be more carefully drafted and documented than prenups. Both parties should have independent counsel, full financial schedules should be attached as exhibits, and the agreement should include recitals confirming that both parties had adequate time to review, consult with advisors, and negotiate terms.

When a Postnup Makes Strategic Sense

After receiving an inheritance. Inheritances are separate property under DRL § 236(B)(1)(d), but they can lose that protection through commingling — depositing inherited funds into a joint account, using them for joint expenses, or mixing them with marital assets. A postnup can explicitly preserve the inheritance as separate property even if some commingling has occurred, preventing the argument that the inherited funds were gifted to the marital estate.

Before or after starting a business. A business started during the marriage is presumptively marital property. Without a postnup, the non-owner spouse has a claim to the business's value, including enterprise goodwill, under equitable distribution. A postnup can establish that the business remains the owner-spouse's separate property, or set a predetermined valuation formula that avoids a costly forensic accounting battle later.

When one spouse's financial situation changes dramatically. A major promotion, stock option grant, career change, or decision for one spouse to leave the workforce to care for children can shift the financial dynamics of the marriage. A postnup lets both spouses agree on how these changes will be treated if the marriage ends, while the relationship is still cooperative.

As a reconciliation tool. Some couples use postnups after a period of marital difficulty as a framework for rebuilding trust. The agreement can address specific financial concerns — "if this happens again, this is the consequence" — while providing both parties with predictability about their financial future.

The Cost of a Postnuptial Agreement

Attorney fees for drafting and reviewing a postnup in New York range from $2,500 to $10,000 per spouse, depending on the complexity of the financial picture. Couples with significant assets, business interests, or multiple properties fall at the higher end. Each spouse needs their own attorney, so the total cost for a properly executed postnup runs $5,000 to $20,000.

That cost is a fraction of the $30,000 to $100,000+ that a contested equitable distribution proceeding can run when the same assets are fought over in Supreme Court without a prior agreement.

Getting Your Financial House in Order First

Whether you are considering a postnup or already heading toward divorce, the foundational work is the same: you need a complete, organized picture of every asset, debt, and income source in the marriage. The New York Divorce Financial Split & Asset Division Guide provides the classification worksheets and financial inventory templates that help you distinguish marital from separate property, calculate the value of complex assets like pensions and business interests, and prepare the documentation that both postnup attorneys and divorce mediators need to do their work efficiently.

See more New York guides →