The Disclosure of Sex Data in Employment Relationships: Reconciling Data Protection and Equality Law in the European Union

Enforcing European Union (EU) equality law at work increasingly requires data broken down by sex, yet the General Data Protection Regulation (GDPR) permits such processing only where it is necessary, proportionate and limited to what the purpose requires. Directive (EU) 2023/970 on pay transparency, transposable by June 2026, and Directive (EU) 2022/2381 on women on boards both assume that employers hold reliable information on workers’ sex, but neither explains how it may lawfully be obtained. Drawing on EU legislation, rulings of the Court of Justice and guidance of the European Data Protection Board, the article applies the four-step proportionality test through doctrinal analysis. It shows that sex-related data is not sensitive data as such but comes under Article 9 GDPR when it discloses gender identity, transition or health; that voluntary disclosure produces incomplete and self-selected datasets; and that anonymized data is too coarse for the mechanisms the directives establish. It concludes that systematic processing of sex-disaggregated data is in principle justified where it serves equality obligations, and it proposes a functional understanding of data minimization, structured disclosure subject to safeguards, reliance on administrative data and clarification at EU level.