Between signals and substitutes: strategic and governance determinants of voluntary sustainability assurance

Abstract

Voluntary sustainability assurance (SA) adoption decisions reflect complex interactions between strategic, structural and relational governance dimensions that prior research has examined in isolation. This study aims to examine voluntary SA determinants through a three-pillar governance framework encompassing the strategic pillar (sustainability strategy), the internal oversight pillar (sustainability committee) and the relational pillar (stakeholder engagement), addressing previously unresolved and contradictory findings within each pillar through a unified empirical framework. Integrating signaling, legitimacy, resource dependence and stakeholder theories, the authors use multivariate logistic regression to analyze 2,142 firm-year observations from European companies spanning 2013–2022. Sustainability strategy is the primary driver of voluntary SA demand, with each one-unit increase in sustainability strategy score raising assurance odds by 74.5%. Moderation analysis reveals a governance paradox: sustainability committees in isolation exhibit significant negative direct effects yet amplify the strategy–assurance relationship under strategic alignment. This contingency mechanism reconciles contradictory prior findings on committee effects. Stakeholder engagement shows a consistent substitution relationship: firms with robust stakeholder dialogue are less likely to demand SA, with this effect operating independently of strategy strength, positioning engagement as an unconditional functional substitute for formal assurance. For managers, SA adoption depends on strategic integration rather than standalone governance structures. Investors should evaluate SA as a signal of strategic maturity and not interpret its absence among high-engagement firms as a governance deficit. Assurance providers should reframe their value proposition toward process-quality validation complementing existing engagement infrastructure. Regulators should account for the substitution effect – requiring targeted mandates for high-engagement firms – and the governance paradox, whereby mandating sustainability committees without strategic alignment requirements risks producing symbolic rather than effective oversight. This study conceptualizes a three-pillar sustainability governance framework integrating strategic, oversight and relational dimensions. It establishes stakeholder engagement as an unconditional functional substitute for formal assurance, identifies a governance paradox in which sustainability committees function as strategic amplifiers rather than independent drivers and reconciles contradictory prior findings on committee effects through a contingency mechanism explaining divergent results across the existing literature.