You will often see the phrase "nuptial agreement". It is the umbrella term for a whole family of agreements couples can make about their finances — and knowing how they fit together helps you choose the right one for where you are now. This guide sets out the main types, how the law treats them, and how to tell which one you need.
The three main types
- Prenuptial agreement (prenup) — made before the wedding (see what is a prenuptial agreement?).
- Postnuptial agreement (postnup) — made after the wedding, at any point in the marriage (see postnuptial agreements).
- Separation agreement — made when a married couple decides to separate (see prenup vs separation agreement).
All three set out how finances should be handled, just at different stages. The prenup is the one most people start with, and for a dictionary-style definition of the terminology see prenuptial agreement meaning.
Related agreements you might meet
A couple of others sit nearby and are easy to confuse with a nuptial agreement:
- Cohabitation agreement — for unmarried couples living together (see prenup vs cohabitation agreement).
- Declaration of trust — recording how a jointly owned property is held (see prenup vs declaration of trust).
- Will — dealing with what happens on death rather than divorce, and working alongside a prenup (see prenups and wills).
How the law treats them
All are "nuptial agreements" and are treated on the same principles: none is automatically binding, but a fair agreement made properly — with disclosure, advice and no pressure — is given significant weight (see are prenups legally binding? and are postnups legally binding?). The same Radmacher test runs through the whole family.
Why couples choose each one
The three main agreements answer different questions:
- A prenup is the natural choice when you have assets, a business, a family inheritance or children from a previous relationship to protect before you marry.
- A postnup suits couples who married without one and now want that clarity, or whose finances have changed — a windfall, a business sale, or the birth of a child (see a postnup after years married).
- A separation agreement records terms when a couple parts but is not yet divorcing, often feeding into a later financial settlement.
Which one do you need?
If you are not yet married, that is a prenup. Already married and want to set things out or update them? A postnup. Separating now? A separation agreement. They are tools for different moments — and couples sometimes use more than one over time, for example a prenup before the wedding and a postnup years later after a big change (see changing a prenup after marriage). If the wedding is very close and time is short, a postnup made calmly afterwards can be the better route than a rushed prenup.
How the three compare at a glance
| Agreement | When made | Typical use |
|---|---|---|
| Prenup | Before the wedding | Protecting pre-marital assets, a business or an inheritance |
| Postnup | During the marriage | Clarity after marrying without one, or after a financial change |
| Separation agreement | On separating | Recording terms before or instead of divorce proceedings |
The pattern is simply a timeline: the same underlying job — deciding how finances are handled — done at whichever stage the couple has reached. Because the Radmacher principles apply across all three, the good practice is identical: disclosure, advice, fairness and no pressure.
Can you have more than one?
Yes, and many couples do over the course of a marriage. A common path is a prenup before the wedding, followed years later by a postnup that updates it after a big change — a house purchase, a business sale, an inheritance or the birth of children (see changing a prenup after marriage). A postnup can sit alongside an existing prenup, either confirming or revising it (see a postnup with an existing prenup). If the relationship later breaks down, a separation agreement can then record the actual terms of parting. Each document builds on the last, which is why keeping them consistent — and revisiting them on major life events — matters as much as getting the first one right.
Where cohabitation agreements fit in
One agreement is often lumped in with the nuptial family but sits firmly outside it: the cohabitation agreement. Because it is for couples who live together without marrying, it is not a "nuptial" agreement at all — there is no marriage for it to attach to. It matters because unmarried couples in England & Wales have far weaker automatic financial rights than married ones (there is no such thing as a "common-law spouse"), so a cohabitation agreement does a different but equally important job (see prenup vs cohabitation agreement). If a cohabiting couple later marries, they can convert their intentions into a prenup before the wedding (see a prenup when already cohabiting).
Nuptial agreements: choosing the right one
"Nuptial agreement" is the umbrella term, and choosing the right one is simply about timing. Not yet married? You want a prenup. Already married and setting things out or updating them? A postnup. A marriage ending? A separation agreement. All three are treated on the same legal principles — not automatically binding, but given weight when fair and properly made — so the good practice is identical across the family.
Documents that work alongside a nuptial agreement
A nuptial agreement rarely stands entirely alone; it works best as part of a small set of documents that cover different eventualities. The most important companion is a will, because a prenup or postnup deals with divorce while a will deals with death — two quite different events, and you generally want both in place (see prenups and wills). Where a couple buys property together, a declaration of trust can record the exact shares in which the home is held, dovetailing with what the nuptial agreement says about it. And for assets held in trust, or expected from a family trust, specialist advice on trusts and prenups may be needed. Seeing the nuptial agreement as one piece of a coordinated plan — rather than a standalone fix — is what makes the whole arrangement coherent and reduces the risk of one document contradicting another.
How a prenup and postnup differ in weight
Although prenups and postnups are judged on the same principles, there is a subtle practical difference worth understanding. A prenup is made before the wedding, when either partner is still free to walk away — which is part of what makes a freely signed one so persuasive. A postnup is made once the couple is already married, when the option of not marrying has gone; this does not weaken it in principle, and some argue it can even strengthen the sense that both partners genuinely chose the terms, but the dynamics of pressure are different and courts are alert to them (see prenup vs postnup). The upshot is that both are worth making and both are given real weight when fair; the choice between them is usually dictated by where you are in the timeline rather than by one being inherently "stronger" than the other (see are postnups legally binding?).
A note on separation agreements
The third member of the family, the separation agreement, deserves a closer look because it operates at a very different moment. It is made when a married couple has decided to part but is not yet divorcing — recording how they will handle the home, finances and arrangements in the meantime. Because it is agreed at the point of separation, when both partners can see their situation clearly, a fair separation agreement can carry considerable weight and often feeds directly into the eventual financial settlement, frequently being converted into a binding consent order on divorce. It shares the same DNA as a prenup and postnup — full disclosure, independent advice and fairness all matter — but it looks backwards at a relationship that is ending rather than forwards at one beginning (see prenup vs separation agreement).
Nuptial agreements: FAQs
What is a nuptial agreement?
The umbrella term for prenups, postnups and separation agreements.
What is the difference between a prenup and a postnup?
Timing — before versus after the wedding (see prenup vs postnup).
Is a separation agreement a nuptial agreement?
Yes — it is made by a married couple about their finances, just at the point of separating (see prenup vs separation agreement).
Are all nuptial agreements legally binding?
None is automatically binding, but each is given weight when fair and properly made (see are prenups legally binding?).
Is a cohabitation agreement a nuptial agreement?
No — it is for unmarried couples, so it sits outside the nuptial family (see prenup vs cohabitation agreement).
Can I have a prenup and a postnup?
Yes — a postnup can confirm or update an earlier prenup as your circumstances change (see a postnup with an existing prenup).
Is a postnup as effective as a prenup?
Both are treated on the same principles and given weight when fair and properly made (see are postnups legally binding?).
Do nuptial agreements deal with what happens on death?
No — that is for a will, which works alongside a nuptial agreement (see prenups and wills).
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.