This report investigates the concept of materiality and how it is used to identify issues for management and disclosure. It is aimed at accountancy professionals and business leaders. It explores the extent to which materiality definitions currently reflect the increasing significance of natural capital as a business issue. A survey of over 200 accountancy professionals, interviews with CFOs/senior management from eight major companies, a disclosure survey of corporate reporting by 40 organisations in specific sectors, and desk-based research into relevant literature and work in the field were all undertaken as part of this work. The report focuses on biodiversity and ecosystems.