Sustainability is an important factor for long-term entrepreneurial success. Company-wide sustainability management is necessary, and requires software support if it is to be conducted efficiently. This paper aims to investigate the approaches and instruments that large-scale enterprises have implemented for a company-wide sustainability management. We conducted a multiple-case study of 20 companies, finding that the selection and deployment of sustainability instruments differed from enterprise to enterprise. However, all the enterprises studied exhibited substantial uncertainty about the extent of possible future governmental regulations that would require existing systems to be adapted, incurring high costs and requiring large resource deployments. As a result, software support for sustainability instruments is often implemented using Excel-based solutions. The lack of governmental regulations clearly constrains the technological development and enhancement of enterprise-wide software support for sustainability management instruments. As long as adequate software support remains unavailable, sustainability instruments cannot be implemented throughout the supply chain.