A prenuptial agreement (prenup) is a smart way to set financial expectations before marriage. However, not all prenups hold up in court. In this guide, we cover what a 'watertight prenup' is, how you can make one and what's key to include.
What is a prenup?
A prenuptial agreement is a legal contract that a couple signs before they get married, setting out what happens to their money, property, and debts if they ever separate. It’s not just for the ultra-wealthy - prenups can benefit any couple by bringing financial clarity and security into a marriage.
A well-structured prenup helps you:
Protect what you own – From savings to property and future inheritances.
Avoid financial disputes – Setting expectations upfront can prevent costly legal battles later.
Clarify debt responsibility – If one partner has loans or credit card debt, a prenup can make sure it doesn’t become a shared burden.
Secure business interests – If you own a business, a prenup ensures it stays separate from marital assets.
Plan for the future – You can include agreements about spousal maintenance and how financial responsibilities will be handled.
What can a prenup cover?
A prenup can outline:
🏡 Property ownership – Who keeps what, including homes, cars, and investments.
📈 Business interests – Ensuring one partner’s business isn’t divided in a divorce.
💰 Savings and investments – How joint and individual accounts will be split.
💳 Debt responsibilities – Preventing one spouse from inheriting the other’s financial liabilities.
🏡 Future inheritances – Protecting money or assets passed down from family.
💵 Spousal maintenance – Agreeing on financial support arrangements if the marriage ends.
What does ‘watertight prenup’ mean?
A watertight prenup is one that’s been carefully drafted, legally sound, and built to hold up in court if ever challenged. Since UK law doesn’t automatically enforce prenups, making sure yours is strong, fair, and legally secure is key. This involves ensuring legal advice is obtained, full financial disclosure is given, and the agreement is fair to both parties.
What can make a prenup as watertight as possible?
To maximise the chances of a prenup being enforced, the following factors are crucial:
1. Independent legal advice for both partners
Each person should get their own family law solicitor before signing. This makes sure:
Both partners fully understand their rights and what they’re agreeing to.
There’s no coercion or unfair pressure - a key factor in whether a court will uphold the prenup.
The agreement is reviewed properly and legally sound.
💡 Why this matters: If only one person gets legal advice, the court may decide the other didn’t fully understand the agreement, making it easier to challenge.
2. Full financial disclosure
Both partners must openly and honestly share their financial situation before signing the prenup. This includes:
All assets (property, savings, investments, business interests).
All liabilities (debts, mortgages, financial commitments).
Any expected future assets (inheritance, business growth, pensions).
💡 Why this matters: If either party hides financial information, the agreement could be ruled invalid in court. Transparency is key.
3. Fair and reasonable terms
A prenup shouldn’t heavily favour one partner or leave the other in financial difficulty if the marriage ends. Courts are more likely to uphold agreements that:
Ensure both partners are treated fairly.
Don’t leave one person in financial hardship while the other walks away with everything.
Are proportionate to the couple’s financial situation.
💡 Why this matters: If a prenup is too one-sided, a court could decide it’s unfair and refuse to enforce it.
4. Signing at the right time
Your prenup should be signed at least 28 days before the wedding. Last-minute agreements can look like one partner was pressured into signing, making them easier to challenge in court. If you can't create a prenuptial agreement, you may want to consider a postnuptial agreement instead.
💡 Why this matters: A prenup signed days before the wedding may be seen as coercion, reducing its legal strength.
5. Regular reviews and updates
A prenup isn’t just a one-time document - it should reflect your current circumstances. Life changes such as:
Having children
Buying property together
Starting or expanding a business
Receiving an inheritance
…can affect what’s fair. Courts are more likely to enforce a prenup that has been updated after major life changes.
Key clauses to consider including
A strong prenup should be clear, fair, and future-proof. Here are some common key clauses that you might want to consider:
Asset division – Who gets what?
Set out who keeps what if you separate, covering property, savings, investments, and valuables.
Debt responsibility – Who covers existing and future liabilities?
Clarify who is responsible for mortgages, loans, and personal debts to prevent disputes.
Spousal maintenance – Will financial support be provided?
Decide if one partner will provide ongoing financial support after a divorce.
Property ownership – Who owns what?
Define ownership of homes, rental properties, and overseas assets to avoid legal battles.
Inheritance protection – Keeping family wealth separate
Ensure inheritances stay with the intended beneficiary and don’t become marital assets.
Business interests – Protecting your company
Prevent one spouse from claiming business shares or profits in a divorce.
Review clauses – Keeping your prenup updated
Schedule regular reviews to update the prenup after big life changes.
How legally binding are prenuptial agreements?
In the UK, prenuptial agreements (prenups) aren’t automatically legally binding - but that doesn’t mean they don’t hold weight. Courts are increasingly upholding prenups, as long as they meet key legal requirements and are considered fair.
Plus, a landmark case, Radmacher v Granatino (2010), changed how UK courts view prenups, making them far more likely to be enforced.
Radmacher vs. Granatino
This high-profile divorce case involved German heiress Katrin Radmacher and her ex-husband, Nicolas Granatino, a French investment banker. Before they married, Granatino signed a prenuptial agreement stating he wouldn’t claim any of Radmacher’s £100 million fortune if they divorced.
When their marriage ended, Granatino challenged the prenup, arguing that it was unfair and should be ignored. However, the UK Supreme Court ruled in favour of Radmacher, stating that prenups should be upheld if freely entered into by both parties and fair at the time of enforcement.
This ruling set a legal precedent, meaning courts now give prenups significant weight - as long as they meet the right legal conditions.
FAQs
Can a prenup be overturned in court?
Yes, a court can disregard or modify a prenup if it’s unfair, signed under pressure, or doesn’t meet legal standards. The agreement must be reasonable and voluntary for it to hold up.
Does a prenup override UK divorce law?
Not completely, but courts will take it seriously if it’s fair, properly drafted, and both partners had legal advice. A strong prenup can influence how assets are divided, but the court has the final say.
Is a prenup valid if one party did not disclose all their assets?
No - full financial disclosure is essential. If one partner hides assets, the court may dismiss the prenup or change its terms. Transparency is key to making it legally strong.
Final thoughts
A watertight prenup provides financial security and clarity, helping couples protect their assets and avoid disputes. While not automatically binding in the UK, a properly drafted prenup that meets legal requirements has a strong chance of being upheld by the courts. Seeking expert legal advice is key to ensuring the agreement is fair, thorough, and enforceable.
