The Supreme Court has unanimously ruled that the legal definition of a woman under the Equality Act 2010 is based on biological sex. This means that, for the purposes of the Equality Act, a person’s gender is the biological sex which they were assigned at birth, rather than the gender as which they choose to live.

There had been a proposed amendment to the Gender Representation on Public Boards (Scotland) Act 2018, which would have allowed trans women (people who were born biologically male but who identify as females) to be classed as women for these purposes. The campaign group, For Women Scotland (FWS), objected to this and launched a judicial review. FWS argued that the Scottish government’s definition of a ‘woman’ should exclude trans women, regardless of whether the individual had a gender recognition certificate (GRC). The inner court of session in Edinburgh agreed with FWS, and Members of the Scottish Parliament (MSPs) revised statutory guidance to follow the Equality Act 2010, which would include transgender women who did have a GRC within the definition of ‘woman’. FWS disagreed with this and launched another judicial review, which was dismissed.

The case was brought to the Supreme Court, which had to decide whether a person with a GRC who identifies as female should be included in the definition of ‘woman’ under the Equality Act. The Supreme Court ruled that such people were not classed as women for these purposes. The judges said that doing so would have made the Equality Act incoherent, as certain issues (such as pregnancy or maternity) can only be interpreted as referring to biological sex.

This means that, under the Equality Act:

• A ‘woman’ is a biological woman or girl (a person born female); and
• A ‘man’ is a biological man or boy (a person born male).

If an individual identifies as trans, they do not change sex for the purposes of the Equality Act, even if they have a GRC. Therefore, for the purposes of interpreting the Equality Act:

• A trans woman is a biological man; and
• A trans man is a biological woman.

What does this mean for employers?

The interim update from the Equality and Human Rights Commission on 25 April 2025 states that:

• In workplaces, employers must provide sufficient single-sex toilets, as well as sufficient single-sex changing and washing facilities, if such facilities are needed. This is the case except where each toilet is in a separate room, lockable from the inside.
• Trans men (biological women) should not be allowed to use the men’s facilities, and trans women (biological men) should not be allowed to use the women’s facilities.
• In some circumstances, trans women (biological men) should not be permitted to use the men’s facilities, and trans men (biological woman) should not be permitted to use the women’s facilities.
• However, there must be facilities available to trans people. Therefore, where possible, mixed-sex toilet, washing or changing facilities in addition to sufficient single-sex facilities should be provided.

The ruling has provided some clarity for employers. For example, it is now clear that in the case of requiring a female employee to do a certain job (for example, working as a counsellor for victims of domestic abuse), an employer would not face a sex discrimination claim by denying a trans woman (biological man) this job.

However, the ruling also raises issues. For example, if a workplace had a trans woman (biological man) who had been using the women’s toilets at work without any issue, this person would now be required to use the men’s toilets (if no mixed-sex facilities were available). If colleagues were not aware of this person’s transgender status, the employer would be faced with the choice of allowing the situation to continue (risking a sex discrimination claim) or forcing the individual to use the other toilets and reveal their trans status to their colleagues, (risking a claim for discrimination on the grounds of gender reassignment). It is hoped that more guidance on such situations will be provided soon.

It is important to note that trans people retain their rights under the Equality Act not to experience discrimination on the grounds of their transgender status. They must not be treated less favourably because of the protected characteristic of gender reassignment, either directly or indirectly.

• An example of direct discrimination would be an employer changing a trans employee’s duties so that they no longer have a public-facing role, because the employer is worried about what clients will think.
• An example of indirect discrimination would be an employer having, for no good reason, very different uniforms for male and female employees. This would mean that a transitioning employee who wished to reassign their gender more discreetly, would be put at a disadvantage as they would have to choose a specific time to change their uniform, and the change would be obvious.

Judge Lord Hodge said, “We counsel against reading this judgment as a triumph of one or more groups in our society at the expense of another, it is not.”

We will keep you updated.

If you have any other questions, please do not hesitate to contact one of our HR Advisors by emailing hr@perspectivehr.co.uk or by phoning 01392 247436