Postnuptial agreements are not automatically legally binding in England and Wales. However, this does not mean that they have no legal effect. A properly prepared postnuptial agreement can carry significant weight if a couple later divorces, and the court may hold the parties to its terms where it is fair to do so.

The key issue is how the agreement was made and whether it remains fair. The court will consider whether each person entered into the agreement freely, understood its implications and had sufficient information about the other's financial position. Independent legal advice is also an important safeguard.

The legal approach to nuptial agreements was established by the Supreme Court in Radmacher v Granatino. The judgment confirmed that courts must give appropriate weight to nuptial agreements, including postnuptial agreements, while retaining ultimate responsibility for deciding a fair financial outcome.

In this guide, the family law experts at JMW will explain when a postnuptial agreement is likely to carry weight, and what families can do to make sure their agreement stands the best chance of offering the intended protection.

For a broader introduction, read our guide to what a postnuptial agreement is. For more on the practical process of creating one, see our guide to how a postnuptial agreement works.

What Does ‘Legally Binding’ Mean for a Postnuptial Agreement?

A postnuptial agreement is different from a court order.

Married couples and those in a civil partnership can use a nuptial agreement to record how they want property, business interests, inheritance and other financial assets to be treated if their relationship ends. However, they cannot privately agree to remove the family court's jurisdiction.

If divorce proceedings arise, the court retains its statutory powers to decide what financial provision should be made. For divorcing married couples, this includes considering the factors set out in section 25 of the Matrimonial Causes Act 1973.

This creates an important distinction:

A postnuptial agreement is not automatically binding on the court, but the court may give substantial or decisive weight to the agreement when reaching its decision.

For that reason, describing postnuptial agreements simply as either ‘binding’ or ‘not binding’ can be misleading. Their legal standing depends on the circumstances in which the agreement was reached and the fairness of giving effect to it.

What Did Radmacher v Granatino Establish?

The leading authority on nuptial agreements is the Supreme Court's 2010 decision in Radmacher v Granatino.

The case itself concerned a prenuptial agreement, but the Supreme Court considered nuptial agreements more broadly. Its judgment expressly describes agreements made before marriage and those made after marriage as forms of nuptial agreement.

The court confirmed two important principles.

First, a couple cannot use a prenuptial or postnuptial agreement to remove the court's jurisdiction over their financial arrangements.

Second, the existence of an agreement should not be disregarded. The Supreme Court established that the court should give effect to an agreement freely entered into by each party with a full appreciation of its implications unless, in the circumstances, it would be unfair to hold the parties to it.

In practice, this means a well-drafted postnuptial agreement can have a considerable influence on a future divorce settlement.

What Makes a Postnuptial Agreement More Likely to Be Upheld?

There is no single formality that makes postnuptial agreements likely to be upheld. Instead, the court looks at the agreement as a whole and the circumstances in which it was reached.

Several factors are particularly important:

Both parties entered into the agreement freely

A postnuptial agreement should represent a genuine agreement between the parties.

If one person was placed under improper pressure to sign, the court may question whether they truly agreed to its terms. This can include circumstances involving coercion or undue influence.

The existence of difficult negotiations does not necessarily mean that an agreement was entered into under pressure. The relevant question is whether each person was ultimately free to decide whether to sign.

This makes the way the agreement is negotiated important. Both parties should have sufficient opportunity to consider the proposed terms and obtain advice before making a decision.

Both parties understood the implications

Each person should understand what the postnuptial agreement means for their financial position.

This includes understanding:

• What assets are covered by the agreement.
• What provision would be made for them if the marriage ended.
• How assets such as businesses, property or inherited wealth would be treated.
• What financial claims or expectations they may be agreeing to limit.

The court will be more likely to give weight to an agreement where the parties made informed decisions rather than signing a legal document they did not properly understand.

Both parties received independent legal advice

Each person should have their own solicitor advising them on the postnuptial agreement.

Independent legal advice allows each party to understand their individual position, the effect of the proposed terms and the implications of entering into the agreement.

It is also an important safeguard if the agreement is later challenged. Evidence that both parties received their own legal advice can support the position that each understood what they were agreeing to and entered into it freely.

JMW's postnuptial agreement solicitors advise on agreements involving circumstances ranging from straightforward financial arrangements to business interests, property portfolios and inherited wealth.

There was appropriate financial disclosure

Each party needs a sufficiently clear understanding of the other's financial position.

Depending on the circumstances, financial disclosure may cover:

• Property and land
• Savings and investments
• Pensions
• Business interests and shareholdings
• Trust interests
• Inheritance and other family wealth
• Debts and liabilities
• Overseas assets

If assets or liabilities have not been disclosed, one party may be able to argue that they could not properly understand the implications of the agreement.

Full and frank financial disclosure is therefore a crucial part of creating an agreement that is more likely to withstand scrutiny.

The terms remain fair

An agreement can satisfy the procedural safeguards above and still face scrutiny over its outcome.

The court's role is ultimately to consider what is fair. A postnuptial agreement cannot guarantee that particular assets will be protected regardless of the financial position in which this leaves the other spouse.

For example, an agreement might identify inherited wealth or a family business as non-matrimonial property. That does not necessarily mean the agreement should leave the other spouse unable to meet their reasonable housing or financial needs.

This balance between respecting the parties' financial arrangements and achieving a fair outcome is central to the court's approach.

What Does the Court Mean by a ‘Fair’ Postnuptial Agreement?

Fairness does not necessarily mean dividing every asset equally.

A postnuptial agreement may specifically have been created because the couple wanted to distinguish between different sources of wealth. For example, they might agree that a business established before the marriage, inherited property or wealth received from family members should be treated differently from assets built up together.

The court can take those intentions seriously. However, it will also consider the wider financial circumstances if the marriage ends.

Relevant issues may include:

• Each person's income and earning capacity
• Their property and other financial resources
• Housing and other reasonable needs
• The length of the marriage
• The standard of living during the marriage
• Financial responsibilities towards children
• Any financial dependence that developed during the relationship
• The nature and source of particular assets and how they have been used during the marriage

These considerations reflect the wider statutory framework used by the court when deciding financial arrangements on divorce.

An agreement can therefore provide substantial asset protection while also making appropriate financial provision for the other spouse.

For example, where one spouse has significant business interests or inherited family assets, a postnuptial agreement might seek to preserve those assets while providing the other person with sufficient property or capital to meet their needs.

The strength of the agreement does not depend on securing the most favourable possible terms for one person. A realistic and fair agreement is generally better positioned to withstand future scrutiny.

Can the Court Ignore or Depart From a Postnuptial Agreement?

Yes. The court retains the power to depart from the terms of a postnuptial agreement when fairness requires it.

This does not mean that a court will routinely disregard agreements when one spouse changes their mind. The purpose of the Radmacher approach is to recognise the importance of agreements that couples have freely and properly made.

However, concerns may arise where:

• One party did not enter into the agreement freely
• Important financial information was withheld
• One person did not properly understand what signing meant
• One party did not receive independent legal advice
• The agreement makes inadequate provision for reasonable needs
• The financial needs of children have not been properly addressed
• The family's circumstances have changed significantly since the agreement was signed

The weight given to these factors depends on the specific circumstances. They do not necessarily mean that the whole agreement automatically becomes invalid.

What Can Make a Postnuptial Agreement Invalid or Ineffective?

People sometimes ask what can ‘void’ a postnuptial agreement. In England and Wales, it is usually more useful to consider what might cause the court to give the agreement less weight or decline to apply particular terms.

Several issues can create difficulties:

Pressure, coercion or undue influence

An agreement entered into voluntarily carries much more weight than one reached because a person felt they had no meaningful choice.

Where there are concerns about coercion, controlling behaviour or domestic abuse, the circumstances in which the document was proposed and signed may therefore be particularly important.

Inadequate financial disclosure

If one party withheld significant assets or provided an inaccurate picture of their financial position, the other person may not have been able to make an informed decision.

This can become particularly significant in high-value cases involving business ownership, trusts, family assets or complex financial structures.

Lack of understanding or independent advice

Failing to obtain independent legal advice does not automatically invalidate an agreement. However, it may make it harder to show that the person fully understood the consequences of entering into it.

Using separate specialist family lawyers allows both parties to make informed decisions and reduces uncertainty around what each understood when signing.

Unfair financial provision

A postnuptial agreement intended to protect significant assets should still consider the reasonable financial needs of both parties.

An agreement that produces a clearly unfair outcome is more vulnerable to the court departing from its terms, even if it was signed voluntarily.

Failure to address children's needs

An agreement between spouses cannot simply override the needs of their children.

Where children are involved, their housing and financial needs form part of the wider assessment of fairness.

Significant changes after signing

An agreement may have been carefully drafted and fair when it was made but become less appropriate over time.

That is one reason why postnuptial agreements should be reviewed rather than treated as documents that can never need updating.

Can a Postnuptial Agreement Become Outdated?

Yes. Financial and family circumstances can change substantially during a marriage.

Events that may justify reviewing an existing agreement include:

• Having or adopting children
• One spouse leaving work or substantially reducing their hours
• A significant change in either person's income or earning capacity
• Receiving a substantial inheritance
• The growth or sale of a family business
• Major changes to property, investments or pensions
• Changes involving trusts or other family wealth
• Moving overseas or acquiring significant international assets

None of these circumstances automatically undermine a postnuptial agreement.

Instead, the question may become whether it would still be fair to hold the parties to the terms they originally agreed.

A well-drafted agreement should contain a review clause identifying events or time periods when the couple should revisit the arrangements. Even where there is no formal review clause, seeking further legal advice following significant changes can help ensure that the agreement remains relevant.

What Happens If One Spouse Challenges a Postnuptial Agreement?

A dispute over a postnuptial agreement will often arise when the couple is negotiating their financial settlement following relationship breakdown.

One spouse may argue that the agreement should largely determine the settlement, while the other may argue that the court should give it less weight or depart from particular provisions.

A challenge may involve questions about:

• The circumstances in which the agreement was made
• Whether either person was placed under improper pressure
• What financial disclosure was provided
• Whether each party received legal advice
• Whether they properly understood the terms
• Whether the agreement makes fair financial provision
• How the family's circumstances have changed since signing

This does not necessarily mean the court will disregard the entire agreement. The court will consider the evidence and decide the appropriate weight to give it within the overall financial proceedings.

JMW advises on disputes concerning both pre- and postnuptial agreements. Our contested nuptial agreement solicitors can advise where you are seeking to rely on an agreement or believe that it should not determine the outcome of your divorce.

Does a Postnuptial Agreement Become Legally Binding When You Divorce?

A postnuptial agreement does not automatically turn into a binding financial order when the marriage ends.

If both parties remain willing to follow the agreement, its terms can provide a framework for negotiating the financial settlement. This may substantially narrow the issues that need to be resolved.

The agreed settlement should then usually be formalised through an appropriate court order.

A financial consent order, once approved by the court, turns an agreed financial settlement into a legally binding court order covering matters such as property, pensions, maintenance and future financial claims.

If one party disputes the postnuptial agreement, the court may instead need to determine what effect it should have within the wider financial settlement.

The distinction is important: the postnuptial agreement records the financial arrangements the couple made during their marriage, while a financial order formalises the financial settlement following divorce.

How Can a Solicitor Strengthen the Position of a Postnuptial Agreement?

The court's approach makes the preparation of a postnuptial agreement particularly important. Simply putting an agreement in writing and signing it does not provide the same safeguards as taking specialist family law advice.

A solicitor can help by:

• Providing independent legal advice, so you understand both your existing rights and the effect of the proposed terms.
• Understanding and analysing financial disclosure, including complex assets where necessary.
• Assessing whether the proposed provisions are realistic and fair, rather than focusing on asset protection in isolation.
• Drafting clear terms, including arrangements relating to property, inheritance, business interests, pensions and trusts.
• Identifying potential areas of challenge, so that they can be addressed while the agreement is being prepared.
• Including appropriate review provisions, particularly where significant future changes can reasonably be anticipated.
• Reviewing an existing agreement, where circumstances have changed since it was signed.
• Advising on contested agreements, where a postnuptial agreement is being relied upon or challenged during divorce proceedings.

JMW's family law team advises on nuptial agreements involving straightforward financial arrangements through to high-value matters involving property portfolios, businesses, inherited wealth, trusts and offshore assets.

Getting the agreement right from the outset can provide greater clarity over your financial future and puts it in a stronger position if it is ever considered by the court.