Prenups: What They Actually Do (and Don't Do)

A prenuptial agreement is, at its core, a contract — one you sign before you get married that tells a court what should happen to your money, your business, your trust distributions, and your debts if the marriage ever ends. For people with significant assets, complex equity comp, family money, or a business they built before meeting their partner, a prenup is rarely about doubting the relationship. It's about deciding now, while you both still like each other, what "fair" looks like — instead of letting a state court figure it out later under default rules that probably don't fit your life.

This guide is what every high-net-worth couple should understand before they sign one. We'll cover what a prenup can and cannot legally do, the state-law landscape, the HNW-specific provisions that actually matter (business interests, trust beneficiaries, RSUs, future inheritance), the single most expensive issue couples miss (active vs. passive appreciation), and how to coordinate the prenup with your estate plan.

Private Wealth Collective is a wealth manager, not a law firm. We don't draft prenups — your family law attorney does. Our role is making sure the prenup, your estate plan, your business agreements, and your investment strategy are all telling the same story. That coordination is where most HNW prenups quietly fall apart.

Prenup vs. Postnup: What's the Difference?

A prenuptial agreement ("prenup") is signed before the marriage. A postnuptial agreement ("postnup") is the same kind of contract, signed after you're already married.

Legally, they do almost the same things — separate vs. marital property, debt allocation, spousal support, business carve-outs. But courts scrutinize postnups more carefully in many states. Once you're married, you owe each other fiduciary duties, and the bargaining power has shifted. Postnups are still widely used and enforceable, but the documentation and disclosure standards are typically higher.

If you're already married and wish you had a prenup — for example, you're about to inherit a large sum, take a company public, or merge a family business — a postnup is usually still the right answer.

What a Prenup Can Do

A well-drafted prenup can:

• Define separate property. Anything you owned before the marriage — investment accounts, real estate, business interests, retirement accounts — stays yours. The prenup makes this explicit instead of relying on tracing rules.
• Carve out a business. Your business interest, including its growth during the marriage, can be designated as separate property. (This is the single most common HNW provision.)
• Allocate debts. Student loans, business loans, prior tax liabilities — the prenup can say who's responsible.
• Address spousal support. In many states, you can waive or limit alimony. Some states won't enforce a total waiver if it leaves a spouse destitute, but reasonable limits are typically honored.
• Protect future inheritance. If you expect to receive distributions from a family trust or an inheritance during the marriage, the prenup can keep that separate.
• Handle equity comp. RSUs, ISOs/NSOs, carried interest, profits interests — all can be addressed before they vest.
• Set sunset clauses. The prenup can automatically expire after a number of years, or convert certain assets to marital property over time.
• Allocate retirement contributions and growth. Especially useful when one spouse has significant pre-marital retirement assets.
• Address pets, art, intellectual property, royalties.
• Choose which state's law applies (within limits — the state must usually have some meaningful connection to the couple).
• Define what happens at death, working alongside (not in place of) wills, trusts, and beneficiary designations.

Infidelity clauses ("if you cheat, you forfeit X") are a common ask. Most state courts won't enforce them, because they're seen as either incentivizing divorce or being punitive in ways family law disfavors. A few states will enforce narrowly drafted versions. Don't make this the centerpiece of your agreement.

What a Prenup Can't Do

There are firm limits.

• Child support and child custody. These are always decided by the court at the time of divorce, based on the child's best interests at that moment. You cannot pre-decide custody or waive child support in a prenup. Provisions that try to are ignored.
• Anything that incentivizes divorce. Courts will not enforce terms that make divorce financially attractive. (This is one reason aggressive infidelity clauses get tossed.)
• Anything unconscionable. If the agreement leaves one spouse destitute, or was so one-sided no reasonable person would have signed it absent coercion, a court can refuse to enforce it. Some states judge unconscionability at signing; others judge it at enforcement (decades later).
• Override the rights of creditors or the IRS. Your prenup is between the two of you. It doesn't bind third parties.
• Replace estate documents. A prenup does not substitute for a will, revocable trust, beneficiary designations, or healthcare directives. It coordinates with them.

The State-Law Landscape

Family law is state law, and the differences matter.

Community property vs. common-law (equitable distribution) states

Nine states are community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. In these states, the default rule is that almost everything earned or acquired during the marriage is owned 50/50, regardless of whose name is on the account. A prenup can override this default — but if you don't have one, the default applies.

The other 41 states (and D.C.) use equitable distribution. Marital property is divided "fairly," which doesn't necessarily mean equally. Courts weigh contributions, length of marriage, earning capacity, and other factors.

A few states — Alaska, Tennessee, South Dakota — allow couples to opt in to community property treatment via a community property trust. This is sometimes used for tax-basis planning, not just divorce planning.

The Uniform Premarital Agreement Act (UPAA)

About half the states have adopted some version of the UPAA (1983) or its updated cousin, the UPMAA (2012). These uniform acts standardize what makes a prenup enforceable: written, signed voluntarily, with adequate financial disclosure. States that haven't adopted the uniform acts still recognize prenups — they just use their own case-law standards.

The practical takeaway: prenups are enforceable everywhere in the U.S., but the rules vary enough that a prenup must be drafted by an attorney licensed in the state where the couple is (or will be) domiciled. A "form" prenup downloaded from the internet, or one written for the wrong state, is likely to be challenged successfully.

HNW-Specific Provisions That Matter

For high-net-worth couples, the standard prenup template doesn't cut it. Here are the provisions that actually move the needle.

Business interests and their appreciation

If you own a business going into the marriage, you'll want it designated as separate property. The harder question: what about the appreciation in the business during the marriage? In most states, growth driven by your active efforts during the marriage can be treated as marital property by default. A well-drafted prenup addresses this directly. (More on this below — it's the single most expensive issue HNW couples miss.)

Family trust distributions and future inheritance

If you're a beneficiary of a family trust, distributions you receive during the marriage may, by default, become subject to division depending on how they're titled and used. The prenup should explicitly identify trust distributions as separate property and address what happens if you commingle them.

Future inheritance works similarly. You can designate that any inheritance received during the marriage stays separate.

Equity compensation: RSUs, ISOs, NSOs, carried interest

Equity comp is messy because it has long vesting horizons that straddle the marriage. A prenup can:

• Treat already-vested equity at marriage as separate.
• Define how unvested equity granted before the marriage is treated as it vests (typically pro-rated by the portion of the vesting period before vs. during the marriage).
• Address whether bonuses, restricted stock, or profits interests granted during the marriage are marital.
• Handle carried interest specifically — including the timing of distributions vs. allocations.

Without a prenup, these questions get litigated at divorce. The numbers can be enormous.

Intellectual property and royalties

For founders, authors, content creators, and inventors: IP created before the marriage is generally separate, but royalty streams that continue during the marriage, or works derived from earlier IP, can become marital. The prenup should be specific.

The Active vs. Passive Appreciation Problem (Read This Twice)

This is the issue that quietly destroys more HNW prenups than any other. It's worth a real example.

Imagine you own a business worth $20 million when you marry. The prenup says the business is your separate property. Fifteen years later, the marriage ends, and the business is worth $80 million. Whose is the $60 million in growth?

In most states, the answer depends on whether the appreciation was passive (driven by market forces, general economic conditions, or external factors you didn't control) or active (driven by your continued labor, decisions, and management during the marriage).

• Passive appreciation generally stays separate. If a tech stock you owned before the marriage triples because the sector ran hot, that growth stays yours.
• Active appreciation is often treated as marital — at least the portion attributable to your effort during the marriage.

For a closely-held business you actively run, courts will frequently treat a meaningful chunk of the appreciation as marital, even if the underlying business interest is separate. The same principle applies to carried interest where you're actively managing the fund, or to a real estate portfolio you actively operate.

Worked example

Sarah owns a software company worth $20M when she marries Alex. She actively runs it for the next 15 years. At divorce, it's worth $80M.

• Without a prenup, or with a poorly drafted one, a court in many states could find that $30-40M of the appreciation is marital — driven by Sarah's active management. Alex could be awarded $15-20M of the business's value (or its equivalent in other assets), even though Sarah owned it before the marriage.
• With a well-drafted prenup that explicitly addresses active appreciation, the entire $60M of growth can be preserved as Sarah's separate property — perhaps with a defined "spousal participation" payout, agreed in advance, to acknowledge Alex's contribution to the household during the same period.

A standard prenup will say "the business is separate property." A good HNW prenup will say "the business and all appreciation thereon, whether active or passive, is separate property" — and back it up with provisions about how Sarah will be compensated for her labor (a market-rate salary paid into the marital account, for instance) to defeat the argument that her active management was uncompensated value flowing to the separate asset.

This single clause is sometimes worth nine figures. It's also the kind of language a $500 template can't write.

Why DIY Prenups Don't Hold Up

The internet is full of prenup templates, and several startup platforms now offer software-driven prenup generation. For very simple situations, they may work. For HNW couples, they almost universally don't, for several reasons:

• Separate counsel. Most states either require, or strongly favor, each spouse having their own attorney. A prenup where both spouses used the same lawyer (or no lawyer) is much easier to challenge.
• Full financial disclosure. Both parties must disclose all assets, income, and liabilities in writing, usually as an exhibit to the agreement. Incomplete disclosure is the single most common reason prenups get voided. Software platforms can't audit your disclosures.
• State-specific drafting. Each state has its own quirks — California requires a 7-day waiting period; some states require notarization; Florida has specific spousal-support waiver rules; New York has its own formalities. A national template often misses these.
• Active appreciation, carried interest, business valuation methods. These require bespoke drafting that no template handles.
• Coordination with the estate plan. Templates don't know what your trust says.

For a couple with a starter home and two W-2 jobs, a software prenup might be acceptable. For a couple with a business, a trust interest, equity comp, or material pre-marital wealth, it is not.

The Disclosure Requirement (Don't Skip This)

Almost every state requires full and fair financial disclosure before a prenup is signed. Both parties must know what they're waiving rights to.

In practice, this means each spouse provides a written schedule of:

• All assets (accounts, real estate, business interests, trust interests, retirement accounts, life insurance cash value)
• All liabilities
• Income from all sources
• Expected inheritances (in some states)

If you hide assets — even unintentionally — a court can void the entire agreement years later. There is no "I forgot" defense.

For complex estates, this typically means attaching tax returns, business valuations, and trust documents as exhibits. Build it once, build it right.

Timing: Do Not Sign Two Weeks Before the Wedding

The single fastest way to make your prenup unenforceable is to drop it on your fiancé the week of the wedding. Courts look at:

• How much time the receiving spouse had to review the agreement.
• Whether they had independent counsel.
• Whether they were under economic, emotional, or social pressure ("sign or the wedding is off").

In some states (California, for example), there is a statutory minimum waiting period between when the agreement is presented and when it's signed. Even where there's no minimum, 30 to 90 days before the wedding is the bare minimum for an HNW agreement. Six months is better. The earlier the conversation starts, the less it feels like an ultimatum.

A prenup signed the day before the wedding is the easiest agreement in the world to challenge for duress.

Sunset Clauses and Periodic Review

Some couples include a sunset clause — the prenup automatically expires after a number of years, or after a triggering event (the birth of a child, a major asset sale, an anniversary). This is a values choice. Some couples want the prenup to fall away over time as the marriage matures. Others want it to remain in force indefinitely. Either is defensible; just decide deliberately.

Separately, every HNW couple should review the prenup every 5-10 years, or after major life events (sale of a business, large inheritance, birth of children, move to a new state). Life facts change. The prenup may need an amendment or restatement.

Integrating the Prenup With the Estate Plan

This is where wealth managers earn their keep, because most family law attorneys do not draft trusts and most estate attorneys do not draft prenups, and the two documents need to agree.

The classic HNW setup is a revocable trust plus a prenup with explicit carve-outs. The trust holds separate property; the prenup confirms that anything in the trust (and anything funded into the trust from separate sources during the marriage) remains separate. Beneficiary designations on retirement accounts and life insurance need to be consistent with the prenup's treatment of those assets. If the prenup says the 401(k) is separate but the spouse is the named beneficiary, you have a contradiction.

When children from a prior marriage are involved, this coordination is non-negotiable. A prenup can protect the assets you intend to leave to your children, and the estate plan operationalizes that intent.

Other coordination points:

• Buy-sell agreements. If you co-own a business, the buy-sell agreement and the prenup must agree on what happens at divorce or death.
• Trust beneficiary designations. If you're a beneficiary of an irrevocable family trust, the prenup should reference that interest and its income stream explicitly.
• Life insurance. Term life used to secure spousal-support obligations should be referenced in both documents.
• SLATs and ILITs. Spousal Lifetime Access Trusts and Irrevocable Life Insurance Trusts have specific divorce-vulnerability issues that the prenup can address.

This is exactly the kind of coordination that benefits from a wealth manager sitting in the same room as the family law attorney and the estate attorney.

Cost Expectations

For HNW couples, expect to spend $5,000 to $50,000+ on a prenup, depending on complexity, jurisdiction, and the amount of disclosure-document preparation involved.

• Simple HNW prenup (one spouse has significant pre-marital assets, no business, no trust interests): $5,000-$15,000 per side
• Business owner with valuation issues: $15,000-$30,000 per side
• UHNW with multiple businesses, trust interests, carried interest, multi-state issues: $30,000-$100,000+ per side

Each spouse pays their own attorney. (Yes, even though only one of you might have most of the assets — courts will scrutinize agreements where the wealthier spouse paid for the less wealthy spouse's lawyer.)

Compared to what's at stake — a contested divorce can easily run seven figures in legal fees, plus the actual asset division — a well-drafted prenup is the cheapest insurance most HNW couples will ever buy.

What If You're Already Married? The Postnup Option

If you're reading this thinking "I should have done this five years ago," you're not out of options. A postnuptial agreement can do most of what a prenup can do, with some important caveats:

• More scrutiny. Postnups are more carefully reviewed by courts because the marriage already exists and the spouses owe each other fiduciary duties.
• Independent counsel is non-negotiable. Both spouses must have their own attorney.
• Consideration. Some states require something of value to be exchanged for the postnup. The marriage itself was the consideration for a prenup; for a postnup, you may need to give up something specific.
• Specific triggers. Common postnup triggers: imminent inheritance, IPO or business sale, second marriage with blended-family planning, reconciliation after separation, or a couple realizing the original prenup is now outdated.

A postnup is harder to enforce than a prenup, but it's still very enforceable when properly done.

Common HNW Mistakes

Patterns we see repeatedly:

1. Treating the prenup as a one-off legal document, not part of the wealth plan. Without coordination, the prenup, the trust, the buy-sell, and the beneficiary designations contradict each other. Litigators feast on this.
2. Inadequate financial disclosure. Trying to "simplify" the disclosure exhibits. This is the most common reason prenups are voided.
3. Ignoring active appreciation. Standard prenup language doesn't address it; HNW prenup language must.
4. Signing too close to the wedding. Five years of careful planning, undone by a 10-day signing window.
5. Using the same attorney as your fiancé. In most states, this is grounds for a successful challenge.
6. Forgetting to update after major events. Birth of children, business sale, large inheritance, move to a new state — all should trigger a review.
7. Trying to over-reach. A prenup that's transparently one-sided invites a court to set it aside on unconscionability grounds. A reasonable prenup is enforceable; a brutal one often isn't.
8. Forgetting beneficiary designations. The prenup says the IRA is separate, but the spouse is still listed as primary beneficiary. The beneficiary designation usually wins.
9. Failing to address what happens at death. Prenups can include "waiver of elective share" provisions where appropriate, but only with proper coordination.

How to Actually Bring It Up

The hardest part of the prenup isn't the legal drafting. It's the conversation.

Some guidance that works:

• Frame it as planning, not distrust. "I want us both to be protected, and I want my [business / trust / family money] to be handled in a way that doesn't blow up our marriage if anything ever happens."
• Start early. Bring it up six to twelve months before the wedding. Not the week of.
• Lead with disclosure. Walk through your full financial picture. Invite them to do the same. The prenup is, in part, just the formal version of the financial conversation every serious couple should have anyway.
• Use professionals. Have your wealth manager or an attorney explain the relevant defaults under your state's law. "Here's what happens by default — is that what we both want?"
• Don't haggle over small things. A prenup is not the moment to optimize for the last dollar. It is the moment to be transparent and fair.
• Acknowledge what the agreement doesn't cover. Love. Time. The actual marriage. You're agreeing about money, not about whether the marriage matters.

For couples coming into second marriages or blending families, the prenup conversation is often easier — both spouses have lived through the alternative and understand the stakes.

When You Need a Prenup, in Order of Priority

You should very seriously consider a prenup if you have:

1. A business (existing or imminent)
2. Material pre-marital wealth ($1M+ in investable assets is a common threshold; in many cities, the bar is lower)
3. Children from a prior relationship whose inheritance you want to protect
4. An expected inheritance of any meaningful size
5. A trust interest you're a current or future beneficiary of
6. Significant equity compensation vesting during the marriage
7. Substantial debt (especially a spouse's pre-marital debt you don't want to inherit)
8. A meaningful income disparity (in either direction)
9. Career sacrifices one spouse is making (which can cut both ways at divorce)

If two or more of these apply, the question is no longer "should we get a prenup?" — it's "what should the prenup say?"

How Private Wealth Collective Fits In

We are not your attorney. We don't draft prenups, postnups, or any other legal document. Your family law attorney drafts the prenup, and your estate attorney drafts the trust. What we do is sit in the middle and make sure every document is telling the same story — that the estate plan, the tax strategy, the business buy-sell, the beneficiary designations, the gifting strategy, and the prenup all reinforce each other instead of working at cross-purposes.

For most HNW couples, the prenup is one document in a multi-document, multi-decade wealth plan. The coordination is where the value is.

If you're getting married, getting remarried, or wishing you'd done this years ago, the right next step is to have someone help you map out the full picture before you start drafting anything. Book a call and we'll walk through where the prenup, the estate plan, and the wealth plan all need to talk to each other.

FAQ

Do I need a prenup if I have a revocable living trust?

Yes — they do different things. The trust governs what happens to assets you put in it (during your life and at your death). The prenup governs what happens at divorce. A trust does not, by itself, protect assets from a divorcing spouse, especially if you've commingled marital earnings into trust assets. The two documents should be drafted with each other in mind.

Can a prenup protect my business if my spouse never works there?

Mostly yes, but not entirely. The business interest itself can be designated as separate. The trickier issue is the appreciation during the marriage — especially if you actively run the business. A well-drafted prenup addresses active vs. passive appreciation explicitly. Without that language, courts in many states will treat at least part of the growth as marital.

Will my prenup hold up if we move to a different state?

It depends. Most prenups include a "choice of law" provision specifying which state's law applies. Courts often (but not always) honor that choice, especially if the state has a meaningful connection to the couple. If you move to a community property state (or out of one), or to a state with very different rules on spousal-support waivers, get the prenup reviewed by a local attorney within the first year.

How long before the wedding should I sign?

At a minimum, 30-60 days. For HNW agreements, 90+ days is far safer. The closer to the wedding, the easier it is to challenge for duress.

Can we use the same lawyer to save money?

Almost never a good idea. Most states require, or strongly prefer, separate counsel. Sharing a lawyer is one of the easiest grounds for a court to find that the less-wealthy spouse wasn't properly represented. Pay for two lawyers; you'll save the cost many times over.

What's the difference between a prenup, a postnup, and a separation agreement?

A prenup is signed before marriage. A postnup is signed during marriage. A separation agreement is signed when the couple is already separating, addressing the actual division of assets and support. All three are contracts; the rules and the scrutiny levels differ.

What if my fiancé refuses?

That's a real conversation, not a legal one. Some people object on principle; others object because they feel the prenup is one-sided or being sprung on them. Slowing the timeline, bringing in independent counsel, and being transparent about disclosure usually moves the conversation forward. If it doesn't — that's also useful information, and a wealth manager or therapist can help you work through what the resistance is really about.

Are infidelity clauses enforceable?

Usually no. Most state courts won't enforce a clause that financially penalizes infidelity, because it's seen as either incentivizing divorce or running afoul of no-fault divorce policy. A few states will enforce narrowly drafted versions. They're not the centerpiece of a serious prenup.