Yes — you can change a prenup after you are married, by making a postnuptial agreement. A postnup is the after-marriage equivalent of a prenup, and it can update, replace or confirm the terms you agreed before the wedding. You do not edit the original document; you make a fresh agreement that reflects where your lives are now.
Why you might want to change it
A prenup is a snapshot of your finances and intentions at one moment. Over a marriage, that picture inevitably shifts, and there are many good reasons to bring the agreement up to date:
- You have had children, changing what is fair for both partners.
- One of you has stopped working to care for the family, becoming a stay-at-home parent.
- Your finances have grown or changed — a business has taken off, you have bought a home together, or received an inheritance.
- The original terms now feel unfair to one of you, and you want to put that right.
- A review clause in the prenup has fallen due and prompted you to look again.
Keeping the agreement aligned with your real circumstances helps it stay fair and effective, because an outdated agreement can carry less weight when a court tests fairness at the date of divorce (see are prenups legally binding? and does a prenup expire?).
How to change a prenup properly
Changing a prenup is not as simple as crossing out a clause or writing in the margin — informal amendments carry little weight and can create confusion about what was actually agreed. Instead, you make a fresh postnuptial agreement following the same good practice that made the original robust:
- Fresh disclosure. Exchange up-to-date full and frank financial disclosure, because your assets have moved on since the wedding.
- Fair terms. Agree terms that are balanced and meet both partners’ needs as they are now.
- Independent advice. Each partner takes their own independent legal advice.
- Proper signing. Execute the postnup as a deed, witnessed, and keep it safely.
Done this way, the new agreement replaces the old one cleanly and stands on the same firm footing (see what to include in an agreement and how to make it fair).
Does a postnup carry the same weight as the prenup?
Broadly, yes. The leading case, Radmacher v Granatino, applies to both prenups and postnups: a court gives effect to an agreement freely entered into with a full appreciation of its implications, unless it would be unfair to do so. A postnup made calmly, without a wedding date looming, can even look particularly free from pressure (see are postnups legally binding?).
How much does it cost to update a prenup?
Updating an agreement is usually no more expensive than making the original, and often less if the bones of the earlier document can be reused. If you prepare the new postnup online for a fixed fee and then have each partner take advice on it, the total is modest compared with the cost of a contested divorce it helps you avoid (see postnup costs and why a prenup is cheaper than a divorce). It is worth budgeting for two rounds of independent advice, one for each of you, because that separate advice is what keeps the updated agreement robust — the same safeguard that mattered first time round (see independent legal advice). Set against the value of the assets a good agreement protects, it is a small, sensible outlay.
Does the update replace or sit alongside the original?
A well-drafted postnup should say clearly that it replaces the earlier prenup, so there is no ambiguity about which document governs. Leaving two agreements in existence, each saying slightly different things, is a recipe for argument later. The new agreement should expressly supersede the old one and deal comprehensively with your current finances, so that anyone reading it — including a court, if it ever came to that — knows it is the definitive statement of what you intend (see a postnup where a prenup already exists). Keep the superseded prenup on file as part of the history, but make sure the postnup is unmistakably the one that counts.
A worked example: from prenup to postnup
Suppose a couple signed a prenup ring-fencing a flat one of them owned before the marriage. Five years in, they sell that flat and put the proceeds into a larger family home they buy together, in joint names. The original prenup now describes an asset that no longer exists in the same form, and says nothing about the new house that has become the centre of their lives. Rather than leave that gap, they make a postnup: they disclose their current finances afresh, agree how the family home should be treated, each take advice, and sign it as a deed. The new agreement reflects reality, which is exactly what gives it weight (see what happens to the house and joint versus separate property).
Common mistakes when updating a prenup
Because it feels like a smaller job than the original, couples sometimes cut corners when changing an agreement. The usual pitfalls are worth avoiding:
- Writing on the original. Annotations, crossings-out and margin notes carry little weight and create confusion about what was actually agreed.
- Skipping fresh disclosure. Your finances have moved on, so relying on the old disclosure schedule undermines the update.
- One partner going without advice. Both should take independent advice on the new terms, just as with the first agreement.
- Leaving it until a crisis. Updating calmly, in a settled marriage, is far stronger than trying to renegotiate when things are already strained (see disagreeing on terms).
What if only one of us wants the change?
An agreement can only be changed if both partners consent — one person cannot rewrite it alone. If one of you feels the current terms have become unfair and the other is reluctant to revisit them, that is a conversation to have openly rather than a change either of you can force. Often the fairest route is to agree in advance, when you first make the prenup, that you will review it after defined events, so updating is expected rather than contested (see the review clause). Approaching it as a shared, forward-looking exercise — not a renegotiation of who gets what — is what keeps both partners on side.
What happens if you leave an outdated prenup as it is?
Nothing dramatic happens overnight, but you carry a quiet risk. Because a court tests fairness at the date of the divorce rather than the wedding, an agreement that no longer matches your lives can be given much less weight — or, in a serious mismatch, set aside on the point that matters most to you. The partner who assumed the old terms still protected their business or pre-marital property may discover, at the worst possible moment, that the court is not persuaded to follow a document that has drifted far from reality (see does a prenup expire? and when is a prenup unfair?). Updating calmly, while you are both content, is the way to keep the protection you paid for actually working. An agreement kept current is far harder to attack than one that has quietly gone stale.
Does updating restart the safeguards?
In effect, yes — and that is a good thing. A fresh postnup is a fresh agreement, so it gets its own round of the things that give a nuptial agreement weight: current disclosure, independent advice for each of you, fair terms and proper execution as a deed. That means any weakness in the original — perhaps advice was rushed, or disclosure was thin at the time — can be cured by doing the new version properly. A postnup made in a settled marriage, with no wedding date bearing down on anyone, can even look particularly free from pressure, which is exactly what a court likes to see (see are postnups legally binding? and duress and prenups). Think of an update not as patching a document but as rebuilding it on firmer ground.
How often should you revisit it?
There is no fixed rule, but a sensible rhythm is to look at the agreement after any major life event and, in the absence of one, every few years. The events most worth acting on are the birth of a child, buying or selling the family home, a significant change in either partner’s income or wealth, receiving an inheritance, or one of you stepping back from work. Building a review clause into the original prenup turns this from an awkward conversation into a pre-agreed housekeeping task, so neither partner feels ambushed when the time comes (see is my prenup still valid?).
How to change a prenup after marriage
If you want to change a prenup once you are married, you do it by making a postnuptial agreement rather than editing the original. A postnup can update, replace or confirm your earlier terms, and it should follow the same good practice — full disclosure, independent advice, fair terms and signing as a deed. Many prenups build in a review clause precisely so that changing the agreement as life moves on is expected and straightforward.
Frequently asked questions
Can you edit an existing prenup?
Not by crossing out clauses — you make a fresh postnup that replaces it (see postnuptial agreements).
When should you change a prenup?
After major changes like children, a house purchase or a big shift in finances (see prenup review clause).
Do we both need advice again to change it?
Yes — each partner should take independent advice on the new agreement, just as with the original (see independent legal advice).
Can we just tear up the old prenup instead?
You can cancel it, but replacing it with an updated postnup is usually wiser than being left with nothing (see cancelling a prenup).
What if only one of us wants to change it?
A change needs both partners to agree; one person cannot unilaterally alter the agreement (see disagreeing on prenup terms).
How much does a postnup cost to update a prenup?
Much the same as a prenup — from a fixed fee online to more via a solicitor (see postnup costs).
Create your prenuptial agreement online
UK Prenup lets couples in England & Wales create a clear, fair prenuptial agreement online from £199, with your document generated instantly as a PDF. 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.