Strictly speaking, a prenup in England & Wales is never “valid” or “invalid” in the way an ordinary contract is, because it is not automatically binding in the first place. So the real question behind “what makes a prenup invalid?” is this: what stops a court giving the agreement weight? Get that right and your prenup does its job; get it wrong and a court may set it aside or ignore parts of it.
Below are the things that, in practice, cause a court to disregard a prenup – and how to steer clear of each one. Encouragingly, none of them is hard to avoid; they are all about doing the groundwork properly.
What makes a prenup valid in England and Wales
There is no statutory form a prenup must take, so "valid" means something different from a signed lease or a will. The test the courts apply comes from Radmacher v Granatino: the court should give effect to an agreement each of you entered into freely, with a full appreciation of its implications, unless in the circumstances prevailing it would not be fair to hold you to it. Six things satisfy that test in practice, and every one of the problems below is the absence of one of them.
First, full and frank financial disclosure from both of you, recorded in a schedule. Second, independent legal advice for each of you, from different solicitors. Third, time: signed well before the wedding, with the Law Commission suggesting at least 28 days. Fourth, no pressure, so that each of you could have walked away. Fifth, fair terms, which above all means the agreement meets both partners' reasonable needs and never tries to settle anything about children. Sixth, proper signing: in writing, signed by both of you in front of an independent witness, usually as a deed. A prenup made that way is in the strongest position the current law allows. What follows is what happens when one of the six is missing.
1. Incomplete financial disclosure
If either partner did not lay out their assets, income and debts honestly, the other could not have fully understood what they were giving up – and the whole agreement becomes vulnerable. Hidden or understated assets are one of the quickest ways to see an agreement disregarded. The fix is straightforward: exchange full and frank disclosure and record it in a disclosure schedule attached to the document. Not sure how to value things? See how to value your assets and the information you will need.
2. No independent legal advice
Legal advice is not strictly compulsory, but its absence is a red flag – particularly where one partner clearly did not grasp the agreement or its consequences. Separate, independent advice for each partner is the safest course, because it directly answers the two most common complaints: “I did not understand it” and “I was pressured into it”. It is also one of the conditions the law reform proposals would make compulsory (see qualifying nuptial agreements).
3. Pressure, duress or undue influence
The agreement must be entered into freely. Threats, an ultimatum, or springing the document on a partner days before the wedding can all suggest it was not. A court will look hard at the circumstances of signing – who proposed it, when, and whether the other partner had a genuine choice. See what counts as duress or pressure and when to sign a prenup for how to stay clear of this.
4. Unfair terms
An agreement that would leave one partner with nothing to live on, or that tries to shut out provision for children, will not be upheld as written. Fairness – and in particular the needs principle – is the line a prenup cannot cross. A prenup that protects specific assets while still treating both partners decently is far more robust than one that tries to take everything (see when is a prenup unfair? and how to make a prenup fair).
5. Trying to decide things a prenup cannot
You cannot use a prenup to fix child maintenance or child arrangements – the court keeps control of anything affecting a child’s welfare (see prenups and children). Nor do lifestyle clauses – rules about chores, weight or behaviour – carry any legal weight. Including such terms does not invalidate the whole document, but those parts simply have no effect.
6. Signing or execution errors
Even a well-drafted, fair agreement can be weakened by getting the formalities wrong. Signing too close to the wedding, or not executing the document correctly as a deed in front of an independent witness, both give a challenger ammunition. Our guide to what a prenup should include covers the substance; how to sign a prenup covers doing the formalities properly.
“Invalid” is usually a spectrum, not a switch
It is worth repeating that a court rarely declares a prenup “void” outright. Far more often it decides how much weight to give it. One missing safeguard might see the agreement given reduced weight; several missing at once – no disclosure, no advice and unfair terms – may see it ignored entirely, as happened in Ipekçi v McConnell. That is why stacking up the safeguards matters: each one you add makes the agreement harder to unpick. See can a prenup be overturned? for how this plays out in practice.
How a court decides how much weight to give an agreement
Rather than asking a simple “valid or void?” question, a court works through the Radmacher reasoning: was the agreement freely entered into, did each partner have a full appreciation of its implications, and would it be fair to hold them to it? Each safeguard you put in place answers one of those questions.
Disclosure and advice go to “full appreciation”; good timing and a calm process go to “freely entered into”; fair terms and provision for needs and children go to “fair to enforce”. Miss one safeguard and the court may still give the agreement real weight; miss several and it can slide from “followed in full” to “ignored entirely”.
That is why the goal is not a single magic step but a stack of safeguards, each making the agreement harder to overturn.
“Invalid” on paper versus weak in practice
People often picture a prenup being declared “void” like a torn-up contract. In family law it rarely works that way. Because the court’s task under the Matrimonial Causes Act 1973 is to reach a fair outcome, an agreement is not so much “valid” or “invalid” as weighty or weak. A prenup that skipped one safeguard is usually not thrown out; it is simply given less influence, and the court fills the gap.
Only where several safeguards are missing at once does an agreement lose weight entirely. So the practical goal is not to chase some notion of technical validity, but to stack up the features that make a court want to follow the agreement. Every safeguard you add moves the needle from “weak” towards “followed in full”.
A worked example of a weak agreement
Imagine one partner owns a successful business worth several hundred thousand pounds but, when drawing up the prenup, describes it only as “my company” with no value and no accounts attached. The other partner, with no solicitor of their own, signs three days before the wedding after the document appears out of nowhere. The terms give the business-owner everything they brought in and the other partner almost nothing.
On divorce years later, this agreement is about as weak as it gets: disclosure was effectively hidden, there was no independent advice, the timing reeks of pressure, and the terms breach the needs principle. A court could give it no weight at all – much as happened in Ipekçi v McConnell.
Now change just the process: full disclosure with accounts attached, a solicitor each, signing six months ahead, and a fair floor for the other partner. Suddenly the very same protection for the business becomes robust. The lesson is that it is usually the process, not the ambition of the terms, that decides whether an agreement stands.
Common mistakes that quietly weaken a prenup
Alongside the big failures, a handful of smaller slips crop up again and again:
- Vague asset descriptions. “Savings” or “my pension” without figures makes it harder to show the other partner truly understood (see valuing assets).
- No plan for the family home. An agreement silent on the house often becomes the flashpoint on divorce.
- Copying a US-style template. A template written for another jurisdiction can miss the very things E&W courts look for (see UK vs US prenups).
- Never revisiting it. An agreement that never changes drifts out of date; a review clause keeps it current.
None of these voids an agreement by itself, but each hands a would-be challenger something to point at – and several together can tip a court towards giving the document little weight.
What makes a prenup invalid: the short version
In short, what makes a prenup invalid – or, more precisely, what stops a court giving it weight – is a missing safeguard: incomplete disclosure, no independent advice, pressure or unfair terms, trying to fix things about children, or getting the signing wrong. None of these is hard to avoid. Get disclosure, advice, fairness and execution right, and there is very little for a court to object to.
What the cases treat as fatal, and what they do not
The decisions since Radmacher v Granatino draw the line in a more forgiving place than the list above might suggest. Versteegh v Versteegh in 2018 is the clearest example: the agreement had been signed the day before the wedding, with no legal advice and no financial disclosure, and the Court of Appeal upheld it because the judge had found the wife understood it and had lived by it.
Missing formalities, on their own, were not fatal; what mattered was whether she had a full appreciation of what she was signing. HD v WB in 2023 shows the other side. The agreement there had no vitiating factor at all, but by the divorce it made no fair provision for the husband's needs, and the judge departed from it to the extent needs required.
In practice, then, an agreement is rarely thrown out; it is followed in full, followed with an adjustment, or given reduced weight on the point where it fails.
Two things are void as a matter of statute rather than weight. Section 34 of the Matrimonial Causes Act 1973 makes void any term that tries to restrict the right to apply to the court for financial provision, but only that term; the rest of the agreement stands. And a clause fixing child maintenance runs into section 8 of the Child Support Act 1991, which keeps that calculation with the Child Maintenance Service. Execution errors are different in kind.
A document not signed in the presence of an attesting witness is not a deed under section 1 of the Law of Property (Miscellaneous Provisions) Act 1989, and while it may still be evidence of what the couple intended, it has lost the formal status that tells a court both partners meant to be bound.
What Standish v Standish means for a prenup's terms
The test for whether a court gives effect to a prenup is still Radmacher v Granatino. The Supreme Court's 2025 decision in Standish v Standish answers a different question: what the court shares when there is no agreement. It held that the sharing principle applies to matrimonial property, the wealth a couple build up together, and that property one partner brought into the marriage, inherited or was given is shared only where the couple have treated it as shared over time. Needs still come first, from whichever kind of property can meet them.
For a couple making a prenup that cuts both ways. The law now starts closer to where most agreements end up, so an agreement that keeps pre-marital and inherited property separate asks the court for less. But whether an asset has become matrimonial is a question of fact, argued years later, and a prenup is the one document that records what you both brought in and what you agreed to treat as shared. The Law Commission's financial remedies scoping report, published in December 2024, set out models for reform with rules on nuptial agreements among them, and in June 2026 the Ministry of Justice consulted on making qualifying nuptial agreements binding (consultation CP 1581, closed 14 August 2026); none of this has yet become law. Our guide to what Standish v Standish means for prenups has the detail.
What makes a prenup invalid: FAQs
Can a prenup be thrown out completely?
A court can decline to follow one that is unfair or improperly made, though it more often gives it reduced weight than throws it out entirely (see can a prenup be overturned?).
Does a small mistake invalidate a prenup?
Not usually – it is the big safeguards (disclosure, advice, fairness, proper signing) that matter most. A minor drafting slip rarely sinks an otherwise sound agreement.
Is a prenup invalid if only one partner had a solicitor?
Not automatically, but it is much weaker – independent advice for each partner is far safer (see do both partners need a lawyer?).
Does an unsigned or unwitnessed prenup count?
An unsigned agreement carries little weight. Executing the prenup as a deed before an independent witness is good practice and the form the Law Commission recommended, but a signed agreement that was freely entered into with a full appreciation of its implications can still be given weight.
Can lifestyle clauses make a prenup invalid?
No – unenforceable lifestyle clauses simply have no effect; they do not poison the rest of the agreement.
Is a DIY prenup more likely to be invalid?
It can be – a DIY prenup that skips disclosure, advice or correct signing is far more exposed than a professionally structured one.
What makes a prenup valid in England and Wales?
Full disclosure, independent advice for each partner, signing in good time without pressure, terms that meet both partners' needs, nothing about children, and proper witnessed signing. Together they satisfy the test in Radmacher v Granatino, and a court gives an agreement made that way significant weight.
When might a UK court refuse to follow a nuptial agreement?
Where one partner did not enter it freely, where there was a material lack of disclosure, information or advice, where it would leave a partner in real need while the other has plenty, or where it tries to prejudice a child's reasonable requirements. Even then the court usually departs from the agreement only as far as fairness requires (see when is a prenup unfair?).
Create your prenuptial agreement online
UK Prenup lets couples in England & Wales create a prenuptial agreement online, with an independent family-law solicitor's advice before you sign: £750 for one of you, or £1,300 with a solicitor for each of you. See how it works or get started.
UK Prenup is not a law firm and does not provide legal advice. A prenuptial agreement in England & Wales is not automatically binding, and both partners should take independent legal advice before signing.