The definition of a woman: what do employers need to know?

On 16 April 2025, the UK Supreme Court delivered a landmark judgement in For Women Scotland Ltd v The Scottish Ministers [2025] UKSC 16. The case concerned the widely debated question: how should the terms “sex”, “man” and “woman” be interpreted under the Equality Act 2010?

The legal background

There are three main statutes at the heart of this claim:

• The Equality Act 2010, which renders it unlawful to discriminate on the basis of protected characteristics. One of those characteristics is sex (being a “man” or a “woman”). Another protected characteristic is “gender reassignment”.
• The Gender Recognition Act 2004 (GRA 2004), which states that an adult who is living in a gender different from their birth gender may apply for a Gender Recognition Certificate. The Act says that once a Gender Recognition Certificate has been issued, the “person’s gender becomes for all purposes the acquired gender” but also that this could be disapplied by other legislation.
• The Gender Representation on Public Boards (Scotland) Act 2018 (2018 Act), the purpose of which was to increase the representation of women on public boards. This Act introduced a target that 50% of the non-executive members of public boards should be women.

The challenge

The appeal to the UK Supreme Court arose in a legal challenge by For Women Scotland, a feminist voluntary organisation, against statutory guidance issued by the Scottish Government under the 2018 Act, defining what a “woman” was for the purposes of the requirement in relation to membership of public boards.

The guidance (the 2^nd version following an earlier successful judicial review challenge by For Women Scotland)  stated that for the purposes of the 2018 Act, a woman was as defined in the Equality Act 2010, and, importantly for the dispute that followed, that this would include a trans woman (i.e. a biological male) with a full Gender Recognition Certificate.  For Women Scotland challenged the guidance on the basis that, correctly interpreted, the definition of a “woman” under the Equality Act 2010, and therefore also the 2018 Act, referred to biological sex only.

The core issue was therefore the question of whether the Equality Act’s use of the terms ”man” and ”woman” includes trans individuals with Gender Recognition Certificates, or whether those terms must be grounded in biological sex. In other words, is a trans woman with a Gender Recognition Certificate a ”woman” for the purposes of the Equality Act?

The arguments

For Women Scotland argued that the Equality Act would be unworkable if a trans woman with a Gender Recognition Certificate was to be considered a “woman”.  They argued, among other things, that if a trans man (born a woman) was to be considered for all purposes a “man”, this would exclude him from the protections of pregnancy and maternity discrimination provisions, which cannot have been the intention of the legislation.

The Scottish Government argued that it was a matter of statutory interpretation and given that the Equality Act was passed after the GRA 2004, it was Parliament’s intention that a “man” should include trans men with Gender Recognition Certificates and a “woman” should include trans women with Gender Recognition Certificates.

Supreme Court Decision

In a unanimous decision, the Supreme Court ruled that sex in the Equality Act refers to biological sex, not certificated sex. In other words, under the Equality Act, a “man” is a biological man, and a “woman” is a biological woman. Accordingly, a trans man (born a woman) is to be treated as a woman under the Equality Act and a trans woman (born a man) is to be treated as a man.

The Court said that any other interpretation would make the Equality Act incoherent and impracticable to operate, therefore the Equality Act disapplied the “for all purposes” provision in the GRA 2004.

The Supreme Court considered that, for example, it would be incoherent for the terms “man” and “woman” to mean anything other than biological sex as the pregnancy and maternity protections afforded under the Equality Act could only make sense if sex has its biological meaning.

A further reason for the Supreme Court’s decision was the privacy implications. If only trans people who had Gender Recognition Certificates were to be considered their acquired gender, this would create two sub-groups of trans people. A certificated trans man would be considered a “man” under the Equality Act, but a non-certificated trans man would not be. This, in turn, would create problems for employers as they would be required to ask the individual whether they had a Gender Recognition Certificate, which could encroach on the individual’s right to privacy and data protection.

The Court concluded there was no good reason Parliament would have intended such confusion, especially for legislation that is meant to be clear and workable in everyday situations.

The Court stressed that its decision would not remove protections from trans people as they, in most cases,

1. have the protected characteristic of gender reassignment and
2. are also protected from discrimination on the basis of their perceived (Direct sex discrimination is prohibited if it is “because of  sex” and harassment is unlawful if it is “related to sex” – these definitions are not limited to the victim’s legally recognised sex.)

In other words, a trans woman could still a claim of discrimination on grounds of transgender status and, although she would not meet the definition of a woman under the Equality Act, she could still potentially bring a claim of sex discrimination in relation to her acquired gender if that was the basis on which she was treated unfavourably.

There should therefore be no sea change in terms of the legal protections available to trans men or women who are subject to harassment or discrimination related to their gender reassignment, or to their perceived sex.

Implications for employers

This decision will have significant implications for women and transgender individuals in the workplace. It has clarified that trans women (whether or not they have a Gender Recognition Certificate) have no legal right to use single sex spaces provided for women, such as the women’s toilet at work. Nor will they be entitled to undertake a job where there is a requirement that the worker must be a woman.

Where an employer decides to permit a trans woman to use a single sex “female space” the employer will incur the risk of sex discrimination claims from biological women.

Many employers are already urgently reviewing their approach to single sex spaces. They will need to consider not just the implications of this judgement but, for example, the Workplace (Health, Safety and Welfare) Regulations 1992 and the relevant HSE Guidance, which deal with the provision of separate sanitary conveniences for men and women. Employers should also take into account that there are women and others, such as observant religious people, who will not feel comfortable using mixed sex toilets and washing facilities, giving rise to potential discrimination claims. The Chair of the Equality and Human Rights Commission (EHRC) has suggested that transgender persons should campaign for “third spaces”, i.e. gender neutral/mixed sex facilities.

The practical ramifications of this decision will require to be worked through. The EHRC is urgently preparing revised guidance in light of the judgment. Employers should consider reviewing their DEI policies and training materials and whether they can provide gender-neutral third spaces, in addition to single sex spaces, where they do not presently have these in place.

In doing so, it will be important for employers to be mindful of the protections which are afforded to women (and men) on the basis of their biological sex, the protections which are still afforded to transgender people, and also whether any of the other protected characteristics are engaged in any given situation.

If in doubt, seek advice from our team of employment law experts at BTO.

This update contains general information only and does not constitute legal or other professional advice.

Douglas Strang, Legal Director: dst@bto.co.uk / 0141 673 2412