Nayyars Solicitors · Family Law Guide
Prenup vs Postnup vs Cohabitation Agreement: Which Do You Need?
Whether you are planning a wedding, already married or living together, you may have wondered whether you should put something in writing about your finances. It is not the most romantic conversation, but it is one of the most sensible, and it can save a great deal of stress and cost if the relationship ends.
The three main options are a prenuptial agreement, a postnuptial agreement and a cohabitation agreement. They do similar jobs, but they apply to different couples at different stages, and the law treats them in different ways. Choosing the right one depends mainly on whether you are married, about to marry or living together.
This guide compares a prenup vs a postnup vs a cohabitation agreement, explains how binding each one is in England and Wales, and helps you work out which is right for you. Our family law solicitors draft all three, so we have set out the practical differences as clearly as we can.
- A prenup is made before marriage or civil partnership, a postnup after, and a cohabitation agreement by unmarried couples who live together.
- Prenups and postnups are not automatically binding, but courts usually follow them if they are fair and properly made.
- A properly drafted cohabitation agreement is generally treated as a binding contract.
- No agreement can limit what is needed for children.
- If cohabiting partners later marry, they should replace their cohabitation agreement with a prenup or postnup.
Prenup vs postnup vs cohabitation agreement: compared
| Prenup | Postnup | Cohabitation agreement | |
|---|---|---|---|
| Who it is for | Couples about to marry or form a civil partnership | Couples already married or in a civil partnership | Unmarried couples living together |
| When it is signed | Ideally at least 28 days before the wedding | Any time during the marriage | Before or during cohabitation |
| Legal status | Persuasive; usually followed if fair | Persuasive; usually followed if fair | Generally enforceable as a contract |
| Court can override? | Yes, if unfair or needs not met | Yes, if unfair or needs not met | Only on normal contract grounds |
| Children | Cannot limit children's needs | Cannot limit children's needs | Cannot limit children's needs |
Prenuptial agreements
A prenuptial agreement, or prenup, is signed before a marriage or civil partnership. It sets out how money, property and other assets will be divided if the relationship ends. Couples often use one to protect a business, an inheritance, family wealth, or property owned before the marriage.
Prenups are not automatically binding in England and Wales, because the court keeps the final say on how assets are divided on divorce. However, since the Supreme Court decision in Radmacher v Granatino in 2010, courts will usually follow a prenup that both people entered into freely, with a full understanding of its effect, unless it would be unfair to hold them to it.
To give a prenup the best chance of being upheld, each person should take independent legal advice, both should give full financial disclosure, it should be signed at least 28 days before the wedding, and its terms should meet both people's needs and those of any children. Our prenup and postnup solicitors build these safeguards in from the start.
Postnuptial agreements
A postnuptial agreement, or postnup, does the same job as a prenup but is made after the wedding. The courts treat it in the same way, so the same safeguards apply.
Couples often make a postnup when something changes: one partner receives an inheritance or starts a business, they move to England from a country where marriage contracts are common, they want to update an old prenup, or they have been through a difficult patch and want clarity going forward. A postnup can also be useful where a couple ran out of time to sign a prenup before the wedding.
Cohabitation agreements
A cohabitation agreement is made between unmarried couples who live together or are about to. It can cover who owns what, how the home is held, how bills and the mortgage are shared, and what happens to property, savings and belongings if you separate.
Cohabitation agreements are especially important because there is no such thing as common law marriage in England and Wales. Unmarried partners do not have the same rights as spouses on separation, so without an agreement, you may have no claim to a home in your partner's name or to their savings and pension. If you buy a home together, a declaration of trust, which records each person's share of the property, often sits alongside the agreement. Our cohabitation agreement solicitors can prepare both.
How binding is each agreement?
The key difference is the court's power to step in. On divorce, the court has a duty under the Matrimonial Causes Act 1973 to reach a fair outcome, and spouses cannot remove that power by agreement. So a prenup or postnup is a very important factor, often the deciding one, but the court can depart from it if it would be unfair, particularly if one person would be left unable to meet their needs.
Unmarried couples do not have that framework, so a cohabitation agreement is generally treated like any other contract. If it is properly prepared, ideally as a deed, with legal advice and honest disclosure, it is likely to be enforced on its terms. It can still be challenged on normal contract grounds, such as pressure, misrepresentation or a lack of understanding.
For all three, the arrangements for children are always decided by what is best for them, and no agreement can stop a parent claiming child maintenance or financial support for a child.
Which agreement do you need?
If you are engaged or planning a civil partnership, a prenup is the right choice. If you are already married or in a civil partnership, you need a postnup. If you live together without being married, or are about to move in, a cohabitation agreement is the one for you.
Your circumstances can change, and your agreement should keep pace. If cohabiting partners later decide to marry, their cohabitation agreement will no longer give full protection, because marriage brings the court's wider powers into play, so they should replace it with a prenup. Any agreement should also be reviewed after major events, such as having children or a significant change in finances.
Where there is significant wealth, a family business or assets in more than one country, it is worth taking advice from our high net worth family lawyers, as the agreement may need to work alongside trusts or foreign law. It is also sensible to review your Wills at the same time, so your agreement and your estate plans work together.
Could the rules change?
Possibly. In June 2026, the government launched a consultation called A Fairer End to Relationships, which closed on 14 August 2026. It proposes "qualifying nuptial agreements", which would make prenups and postnups that meet set conditions legally binding, and explores new rights for cohabiting couples on separation.
Until any new law is passed, the current rules apply, so the best protection remains a carefully drafted agreement made under today's safeguards.
Frequently asked questions
What is the difference between a prenup and a postnup?
The only real difference is timing. A prenup is signed before a marriage or civil partnership, and a postnup is signed afterwards. The courts in England and Wales treat both in the same way.
Is a cohabitation agreement legally binding?
Generally, yes. A properly prepared cohabitation agreement is treated as a contract and is likely to be enforced, provided both partners entered into it freely, with full information and ideally independent legal advice.
Does a cohabitation agreement still apply if we get married?
It will not give you full protection after marriage, because the court then has wider powers to divide assets on divorce. Couples who marry should replace their cohabitation agreement with a prenup or postnup.
Can a prenup or cohabitation agreement cover children?
Agreements can record your intentions, but they cannot limit child maintenance or override what is best for the children. Arrangements for children are always decided by their welfare.
Your Next Steps with Nayyars Solicitors
Not sure which agreement is right for you? We will explain your options in confidence and draft an agreement that gives you real protection.
→ Prenuptial agreements
→ Postnuptial agreements
→ Cohabitation agreements and declarations of trust
→ Reviewing existing agreements
Conclusion
The choice between a prenup, a postnup and a cohabitation agreement mainly comes down to where you are in your relationship. Prenups and postnups protect married couples and civil partners, and courts usually follow them if they are fair. Cohabitation agreements protect unmarried couples, who otherwise have very limited rights, and are generally enforced as contracts.
Whichever you need, the protection comes from doing it properly: independent advice, full disclosure, fair terms and regular reviews as life changes.
This article is for general information only and does not constitute legal advice. Every case depends on its own facts, so please contact Nayyars Solicitors for advice specific to your situation.
