["British Journal of Management, EarlyView. ", "\nAbstract\nConsumer complaints incorporate consumers in value co‐creation with firms. As a pivotal HRM practice, the spillover effects of corporate overtime on consumer feedback warrant rigorous investigation. Using a sample of Chinese A‐share listed companies from 2018 to 2023, this study constructs a firm‐level overtime indicator based on daily satellite nighttime light data and machine learning methods, and analyses over 16 million consumer complaint behaviours. Drawing on the organizational slack theory and job demand control theory, the findings indicate that corporate overtime significantly increases consumer online complaints, mediated primarily through weakened firm–employee relationship and compromised product quality management. Under the ability–motivation–opportunity framework, we demonstrate that employee training (ability), female core employees (motivation) and employee engagement (opportunity) effectively mitigate the adverse effects of overtime. From the perspective of labour–product market interaction, this study deepens our understanding of the literature on firms’ intangible slack resources, employee strain and consumer voice.\n"]