What is adultery?

What is adultery

In everyday terms, adultery is often understood as a partner being unfaithful.

In legal terms, however, adultery had a much narrower meaning. Traditionally, it referred to a married person having sexual intercourse with someone of the opposite sex who was not their spouse.

This means that many behaviours people may see as betrayal, such as emotional affairs, messaging someone intimately, or forming relationships online were not legally classed as adultery. This gap between legal definitions and personal experience often causes confusion.

How the law defines adultery

The legal requirement for intercourse

Under English law, adultery required sexual intercourse between a married person and someone of the opposite sex outside the marriage.

This meant:

• The act had to involve sexual intercourse
• Kissing did not meet the legal definition of adultery
• Messaging, emotional connections or online relationships did not meet the definition
• Adultery could not include non‑physical forms of intimacy

Because the definition was so narrow, adultery was often difficult to prove. In many cases, it relied on one partner admitting the relationship or on clear evidence, which was not always easy to obtain.

Why same-sex interactions were not classed as adultery

Historically, the legal definition also excluded same-sex relationships.

If a married person had a sexual relationship with someone of the same sex, this was not legally considered adultery. Instead, it would usually have been addressed under unreasonable behaviour, a broader category used in divorce proceedings.

This reflected how the law operated at the time, but it also meant the definition did not reflect modern relationships.

Adultery vs infidelity

Although often used interchangeably, adultery and infidelity are not the same.

• Adultery is a legal term with a strict definition.
• Infidelity is a broader term used to describe emotional, romantic, or physical unfaithfulness.

This includes what is often referred to as an emotional affair, a close personal or romantic connection that may not involve physical intimacy but can still feel like a significant breach of trust.

Many situations’ people experience as “cheating”, particularly online infidelity would therefore be considered infidelity rather than adultery.

Examples of infidelity that are not legally adultery

These can include:

• Kissing or physical intimacy without intercourse
• Emotional affairs or close romantic connections
• Messaging or forming relationships online
• Using dating apps while married

While these behaviours can be deeply upsetting, they were not classed as adultery under the law.

What counts as unreasonable behaviour

Before no-fault divorce, these kinds of situations were commonly cited as unreasonable behaviour when applying for divorce.

This category covered a wide range of actions that made it difficult for a couple to stay together, even when adultery could not be proven or did not apply.

Does online or virtual cheating count as adultery

No, online or virtual relationships are not considered adultery in legal terms.

This includes:

• Sending intimate or sexual messages
• Forming emotional relationships online
• Engaging in “cyber” or virtual relationships

Although often described as cheating, these behaviours are classed as online infidelity rather than adultery.

For many people, this is where the law can feel out of step with real life because online or emotional relationships can feel just as serious, even though they are treated differently in legal terms.

Is adultery still relevant under no-fault divorce

Adultery is no longer relevant when applying for a divorce in England and Wales.

Since 6 April 2022, the introduction of no-fault divorce means:

• You do not need to give a reason for the divorce
• You do not need to prove adultery, infidelity or behaviour
• The only legal ground is the irretrievable breakdown of the marriage

This means that even if adultery has occurred, it does not need to be included in your application or considered by the court.

These changes were designed to reduce conflict and remove the need for couples to assign blame during separation.

Does adultery affect divorce fees or financial settlements

Adultery does not usually affect the financial outcome of a divorce.

When decisions are made about finances, the focus is on practical factors, including:

• Each person’s financial needs
• Income, assets and earning capacity
• Arrangements for any children

Infidelity, including adultery, is not generally taken into account when reaching a financial settlement.

There is also no automatic rule that an unfaithful partner must pay divorce costs. Fees are usually paid by the person applying or shared when the application is made jointly.

Does adultery affect child arrangements

Adultery does not usually affect decisions about children.

When deciding child arrangements, the court’s priority is the child’s best interests, including their wellbeing, stability and relationships with both parents.

In most cases, children will continue to have contact with both parents, regardless of whether one partner has been unfaithful.

Only in more serious situations, where a child’s welfare may be at risk, would personal behaviour become a significant factor.

How Slater and Gordon can help

Relationship breakdowns can be complex and emotionally challenging, particularly where trust has been affected.

Although adultery no longer forms part of the legal process, our team can provide clear, practical guidance, explain how the law applies to your situation, and advise on the strength of your position.

For guidance, speak to our family law team.