Book excerpt: This book deals with the limitations of economic and financial accounting as an appropriate instrument to reflect the real value created or destroyed by an organization. The authors present a sustainable social accounting approach that considers both the social and economic value – Blended Value – generated by an organization for all of its stakeholders. This approach is based on four major theories – Stakeholder Theory, Action Research, Phenomenological Perspective and Fuzzy Logic – and was developed on the basis of a cost-benefit analysis.