Biological definition of ‘sex’ in the Equality Act 2010 

The Supreme Court decision in For Women Scotland Ltd v The Scottish Ministers [2025] UKSC 16 has important implications for employers in complying with their obligations under the Equality Act 2010. 

Facts of the case 

For Women Scotland Ltd (FWS), a feminist campaigning organisation, brought judicial review proceedings to challenge the definition of ‘woman’ in the Gender Representation on Public Boards (Scotland) Act 2018 (the 2018 Act).  

The 2018 Act requires positive action to be taken to redress gender imbalances on public sector boards in Scotland, with the aim of ensuring that 50% of non-executive members on public boards are women. The definition of ‘woman’ in the 2018 Act included trans women who had the protected characteristic of gender reassignment and who were living as women.  

FWS argued that this definition was outside the legislative competence of the Scottish Parliament and brought judicial review proceedings. Following a decision of the Inner House of the Court of Session in 2022, revised statutory guidance was produced which stated that the meaning of ‘woman’ was the same as in the Equality Act 2010 (EA 2010) and that a person who has obtained a full gender recognition certificate (GRC) has the sex of their acquired gender.  

FWS brought further judicial review proceedings in relation to the revised guidance, claiming that the definition of ‘woman’ in the EA 2010 should be taken to refer to a biological woman. 

Supreme Court decision 

The Supreme Court had to determine whether the definition of ‘woman’ in the 2018 Act, which included trans women with a GRC, was consistent with the EA 2010 and the Gender Recognition Act 2004 (GRA 2004). 

The Court emphasised that its role was to interpret the words used by Parliament in the EA 2010 and GRA 2004. The principal question to determine was whether the EA 2010 treated a trans woman with a GRC as a woman for all purposes within its provisions. 

The Court concluded that the terms ‘woman’, ‘man’ and ‘sex’ in the EA 2010 referred to a person’s biological sex. This interpretation was necessary to maintain the coherence and workability of the EA 2010. The Court found that interpreting ‘sex’ to include certificated sex (the sex recorded on a GRC) would lead to incoherent and unworkable results in various provisions of the EA 2010.  

The Court highlighted that provisions in the EA 2010 relating to pregnancy and maternity, single-sex services, and positive action measures for women, were predicated on biological sex. Including trans women with a GRC in the definition of ‘woman’ would undermine the purpose of these provisions. It rejected the suggestion that ‘women’ and ‘sex’ could refer to biological sex in some sections of the EA 2010 and certified sex in others. The Court held that the meaning must be consistent throughout in order that employers and others subject to obligations under the EA 2010 can perform their obligations in a practical way.  

The Court noted that the EA 2010 provided separate protections for gender reassignment, which did not depend on the possession of a GRC. It emphasised that trans people are still protected from discrimination under the EA 2010 without needing to redefine ‘sex’. 

The Birketts view 

Lord Hodge gave an express warning against reading the Court’s judgment as a “triumph of one or more groups in our society at the expense of another”. Employers should continue to ensure that trans employees, with or without a GRC, are protected from discrimination and harassment under the protected characteristic of gender reassignment. This protection starts from the point at which the individual is proposing to undergo gender reassignment. Trans people have strict privacy rights in relation to their previous gender, and they will also continue to be protected from discrimination and harassment due to their perceived sex.  

Following the Supreme Court’s decision, employers must ensure that their practices comply with both the EA 2010 and the GRA 2004. While the GRA 2004 allows for legal recognition of gender reassignment for certain purposes, it does not alter the definition of ‘sex’ for the purposes of the EA 2010. The ruling means that the provision of single sex services or facilities should be based on biological sex. This could include provision for separate changing rooms, toilets and other gender-specific services. It also means that when implementing positive action measures to promote gender equality (for example increasing the number of women in senior roles), employers should focus on biological sex. Employers should review their existing policies and practices to ensure they align with the Court’s interpretation. This may involve updating definitions, training staff, and ensuring that all policies are legally compliant. 

The Equality and Human Rights Commission (EHRC) is currently working on updating its Code of Practice and expects to lay the revised Code before Parliament this summer. In a press statement, it has confirmed that it will incorporate the implications of the Supreme Court’s judgment into the new Code. The Code will provide employers with further guidance on how to ensure compliance with their obligations under the EA 2010, in light of the Court’s conclusions. This guidance will be important to help employers and service providers properly understand their obligations in respect of single sex facilities, and for employers to understand how they should accurately capture employee data and complete gender pay gap reporting and other equality monitoring activities.  

In the meantime, the EHRC has issued an ‘interim update’ on the practical implications of the Supreme Court judgment. This guidance states that in workplaces it is compulsory to provide sufficient single-sex toilets, as well as sufficient single-sex changing and washing facilities where these facilities are needed, unless the facilities are located in lockable rooms (not cubicles) intended for the use of one person at a time. Following the Court’s decision, access to single-sex facilities should be based on biological sex. The EHRC update also states that “where possible, mixed-sex toilet, washing or changing facilities in addition to sufficient single-sex facilities should be provided” and it is likely that many employers will now be exploring how they can provide at least some gender-neutral facilities. 

Employers should be sensitive to the concerns of trans employees in the implementation of any changes resulting from the Supreme Court’s decision, ideally consulting with trans employees in advance of any changes and offering appropriate support. Managers should be provided with guidance on any policy changes and any wider communications to the workforce should be carefully worded.