By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.
The main pros of a prenuptial agreement are control and clarity: it can keep pre-marriage stock, a business interest or a future inheritance separate, set rules for debts, and spare both spouses an expensive fight over what belongs to whom. The main cons are cost, a hard conversation, limits on what it can do (it cannot set child support and it cannot waive a spouse’s right to a 401(k)), and the risk that a poorly signed agreement is thrown out years later. In California and Washington, both community property states, the stakes are higher than in most places, because by default nearly everything earned during the marriage belongs to both spouses equally.
This page looks at the trade-off for high-income W-2 households in those two states: couples marrying with equity compensation already on the table, couples who are already married and wondering about a postnuptial agreement, and parents thinking ahead to how an inheritance for their own children should be protected.
What community property changes for a high-earning couple
In California, “all property, real or personal, wherever situated, acquired by a married person during the marriage while domiciled in this state is community property” (Cal. Family Code §760). Washington’s rule is similar: property acquired after marriage by either spouse is community property unless a statute says otherwise (RCW 26.16.030).
For a household where both spouses earn large W-2 salaries plus RSUs, that default covers almost everything that builds wealth after the wedding: salary saved, 401(k) deferrals, ESPP shares, and RSU grants earned during the marriage. Property each spouse owned before the marriage, and gifts or inheritances received by one spouse, generally stay separate. The trouble is that separate property loses its label easily once it is mixed with community money, and equity grants straddle the wedding date.
A prenup lets the couple write their own rules instead of relying on these defaults. Whether that is worth doing depends on what each person brings in and how lopsided their careers are likely to become.
Prenuptial agreement pros and cons at a glance
| Pros | Cons |
|---|---|
| Keeps pre-marriage stock, vested RSUs and their growth clearly separate | Each spouse typically needs a separate family law attorney, and fees add up |
| Sets in advance how unvested grants that straddle the wedding are split | Waiving community rights in future earnings can cost the lower earner a great deal, especially if one spouse later steps back from work for the kids |
| Protects an expected inheritance or family property from being mixed in | Cannot reduce a child’s right to support |
| Can assign responsibility for student loans or other pre-marriage debt | A prenup alone cannot waive a spouse’s survivor rights in a 401(k); that waiver has to be signed after the wedding |
| Can shorten and cheapen a divorce if one ever happens | Can be set aside if signing rules were not followed or terms are unconscionable |
| Usually involves a full financial disclosure before the wedding, which many couples find useful in itself | Needs revisiting after children, a move between states, or a big change in income |
California’s signing rules: where prenups fail
Most prenups that fail in California fail on process, not on terms. Under Cal. Family Code §1615, a court treats the agreement as voluntary only if, among other conditions:
- the spouse it is enforced against had independent legal counsel when signing, or was advised to get counsel and waived it in a separate writing;
- for agreements signed on or after January 1, 2020, that spouse had at least seven calendar days between first seeing the final agreement and signing it, whether or not they had a lawyer;
- an unrepresented spouse received a written explanation of the rights they were giving up before signing;
- there was no duress, fraud or undue influence.
Two limits apply no matter how well the agreement is signed. A premarital agreement may not adversely affect a child’s right to support, and a spousal support waiver is unenforceable if the spouse giving it up had no independent lawyer, or if it is unconscionable when enforced (Cal. Family Code §1612). In practice, a prenup handed over the week of the wedding is a weak prenup. Starting three to six months ahead is common advice from family law attorneys.
How Washington treats prenups
Washington does not have a statute equivalent to California’s premarital agreement act. Courts review prenups under case law, which generally asks whether the terms are fair to the spouse giving up rights and, if they are not, whether that spouse had full disclosure of the other’s finances, understood the agreement, had independent legal advice and signed voluntarily without time pressure. The practical checklist is the same as in California: early drafts, two lawyers, full asset schedules.
Washington also allows married couples to sign a community property agreement deciding what happens to community property at the first death. It must be in writing and executed and acknowledged with the same formalities as a real estate deed (RCW 26.16.120). This is an estate planning tool rather than a divorce tool, and families with minor children should coordinate it with their wills and trusts.
Worked example: an RSU-heavy engineer marrying a resident physician in California
Assumptions, for illustration only. Maya, 32, is a senior engineer at a Bay Area tech company. On her wedding day she holds $500,000 of vested company stock and an unvested RSU grant, made a year earlier, with $400,000 still to vest over three years. Her fiancé, Daniel, is a second-year resident with $250,000 of medical school loans. Within five years they expect a household income near $1,000,000, two children, and a joint brokerage account funded from both salaries.
Without a prenup. Maya’s $500,000 of vested stock is her separate property, and so is its growth, as long as she keeps it in her own account. Part of the unvested grant is likely to be treated as community because it vests during the marriage; California courts usually split such grants with a time-based formula, and the result depends on the facts of the grant. Daniel’s loans were incurred before the marriage, but payments made from community salary after the wedding are community money being used for his debt. California’s default rule is that, on divorce, the community is generally reimbursed with interest for community payments on a spouse’s education loans when the education substantially enhanced that spouse’s earning capacity, though a court can reduce or deny reimbursement in some cases, for example where the community has already substantially benefited from the education (Cal. Family Code §2641). If Maya ever sells her separate stock and deposits the cash in the joint account, tracing it back to separate property becomes much harder.
With a prenup. The couple can state that the vested stock and all of its growth stay Maya’s, set an agreed split for the straddling grant, and say whether community money used to pay down Daniel’s loans is reimbursed if they divorce (the reimbursement rule in §2641 yields to an express written agreement). What they probably should not do is waive community rights in future salaries. If Daniel later works part-time while the children are young, a waiver of community earnings would leave him with very little of the wealth built during the marriage, and a court may look hard at that kind of term.
What does not change. Daniel will still need to sign a written spousal consent after the wedding if Maya wants to name anyone other than him as her 401(k) beneficiary. Federal regulations state that “an agreement entered into prior to marriage does not satisfy the applicable consent requirements” (Treas. Reg. §1.401(a)-20, Q&A-28). Many couples miss this step.
Already married? Postnuptial agreements and transmutations
Most families reading this married years ago. They can still sign a postnuptial agreement, but in California it faces more scrutiny than a prenup, because spouses owe each other a fiduciary duty of “the highest good faith and fair dealing” and neither may “take any unfair advantage of the other” (Cal. Family Code §721). If one spouse gains from the agreement, a court may presume undue influence, and that spouse has to show the agreement was fair and freely made.
Changing the character of a specific asset during marriage, for example declaring that an inherited account is now community property, is a transmutation. It is valid only if made in writing by an express declaration that is made, joined in, consented to or accepted by the spouse whose interest is adversely affected (Cal. Family Code §852). Retitling a house or brokerage account without that language often does not change ownership the way the couple assumed. Postnups and transmutations most often come up when a family moves its assets into a revocable living trust, so they belong in the same conversation as your estate plan.
Your children’s future marriages: trusts protect better than prenups
For parents of young children, the more important prenup question may be 25 years away: what happens to the money you leave your kids if they marry. An inheritance is separate property in both states, but it stays separate only if your child keeps it apart from community money, and a 30-year-old with a new spouse and a down payment to make often does not.
The more reliable protection is to leave assets in a trust that holds them for the child, with a trustee and written rules, instead of outright. Assets held by a properly drafted trust are generally not the child’s to mix with marital funds. That decision is made in your own estate plan now, and it works whether or not your child later signs a prenup. The same thinking applies to beneficiary designations: naming a trust rather than the child directly is covered in our guide to naming a trust as beneficiary of your brokerage account, and the age at which custodial money passes to a child is explained in what happens to a UTMA when a child turns 21.
Common mistakes
- Leaving the prenup until shortly before the wedding, so that late revisions to the final draft run into California’s seven-day rule and invite a duress argument.
- Incomplete disclosure, such as leaving unvested RSUs, deferred compensation or an expected inheritance off the asset schedules.
- Assuming the prenup covers the 401(k) without a post-wedding spousal consent.
- Commingling: depositing separate stock sale proceeds into a joint account after carefully protecting them on paper.
- Never revisiting the agreement after children arrive, a spouse leaves work, or the family moves between California and Washington.
What to document for your children
Whatever you decide, write down why. A short note explaining how the two of you thought about separate and shared money, and why you chose a trust over an outright gift for the kids, gives your children something a legal document cannot: your reasoning. As Kevin Luu puts it: “Your kids will inherit your money. Will they inherit your judgment?” Keeping that note with your estate documents, and revisiting it as part of your family governance work, is how the thinking survives the paperwork.
Frequently asked questions
What percentage of marriages have a prenuptial agreement?
There is no official government count. The figures that circulate come from private opinion surveys with different questions and samples, so treat any single percentage with caution. The more useful number for a California or Washington couple is the size of the community estate a prenup would govern, which for a household earning $1,000,000 can reach millions of dollars within a decade (for illustration, saving $250,000 a year for ten years adds $2,500,000 before any investment growth).
Are prenup pros and cons the same in the UK?
No. This page covers California and Washington law only. Prenups in England and Wales follow different rules and court practice, and couples with ties to another country need advice from a lawyer licensed there as well as a family law attorney in their US state.
Does a prenup affect our estate plan?
Yes. A prenup that keeps certain assets separate changes what each spouse can leave through a will or trust, and it does not replace beneficiary designations or a post-wedding 401(k) spousal consent. Ask your estate attorney to review the prenup when drafting your trust so the two documents agree.
Next step
If a prenup or postnup is on the table, start by building a complete asset schedule for each spouse: vested and unvested equity with grant dates, retirement accounts, real estate, debts and expected inheritances. That schedule is what both attorneys will need first. This is general education, not legal advice, and the right terms depend on your full picture and should be drafted by family law attorneys licensed in your state. If you want help assembling that picture alongside your trust and beneficiary plan, our Tax & Wealth Assessment starts there.
Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.
Connect on LinkedIn → · About KevinThis is part of how we approach Estate Planning for high-income W-2 families at Bright Advisers.
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