Abstract
This paper examines the legal classification of employee participation in corporate social responsibility (CSR) initiatives organised by employers, focusing on the boundary between work and non-work under European Union labour law. The employment relationship has evolved toward a value-based model in which employees are positioned as stakeholders advancing organisational objectives through volunteering programmes and sustainability initiatives formally characterised as voluntary. The analysis reveals that employee CSR participation has become a structured component of corporate governance, frequently coordinated during paid working hours, integrated into performance evaluation systems, publicly recognised through internal communications, and linked to career advancement. Under such conditions, formal voluntariness conceals organisational mechanisms that constrain employee autonomy and reflect structural subordination inherent in the employment relationship. The study examines whether time devoted to employer-organised CSR activities constitutes "working time" under Article 2(1) of Directive 2003/88/EC. Through systematic analysis of Court of Justice case law, including Simap, Jaeger, Matzak, and BX, the paper demonstrates that the decisive criterion lies in the employee's availability and subordination to the employer's authority. Where employers determine when, where, and how CSR activities occur, where participation is integrated into organisational oversight, and where employees perceive professional consequences for non-participation, the legal criteria of working time are fulfilled. The paper further addresses work intensification accompanying CSR participation, where unchanged contractual duties generate latent intensification through heightened productivity expectations and compressed schedules. This legal qualification carries significant consequences for remuneration, working time limits, and occupational health protection. The analysis contributes to understanding how contemporary corporate practices reshape labour law concepts, arguing that CSR participation materially restricting employees' autonomy should presumptively be classified as working time, preserving protective boundaries essential to employees' fundamental rights.