Cornish, L & Malone, C 2026, 'When 20 hectares costs a million dollars: why spatial integrity matters in mine rehabilitation reporting', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2615_42 (https://papers.acg.uwa.edu.au/p/2615_42_Cornish/) Abstract: Mine rehabilitation reporting underpins regulatory compliance, financial provisioning and long-term closure liability management. Across many jurisdictions, rehabilitation performance and financial assurance calculations rely heavily on spatial datasets used to quantify disturbed and rehabilitated areas. However, the integrity of the spatial data supporting these calculations is not always explicitly assessed, despite its influence on reported rehabilitation progress and closure cost estimates. Small inconsistencies in spatial data management, including projection errors, topology issues, inconsistent digitising practices and misaligned datasets, can introduce discrepancies in calculated rehabilitation areas. In large mining operations, even relatively minor spatial inaccuracies may have material financial implications. This paper examines the role of spatial data integrity in mine rehabilitation reporting through a case study of an operational mine in Queensland, Australia. It illustrates how common geographic information system (GIS) data management issues can propagate through reporting workflows and influence rehabilitation area calculations and associated liability cost estimates. This paper identifies typical sources of spatial error, explores how these issues arise within standard reporting processes, and considers the potential financial and compliance implications associated with inaccurate spatial reporting. A practical framework for improving spatial integrity in rehabilitation reporting is also presented. This includes recommended GIS governance practices, quality assurance procedures and data management standards that can be implemented within existing mine reporting systems. Strengthening the spatial foundations of rehabilitation reporting has the potential to improve the reliability of closure metrics, reduce financial uncertainty and support greater confidence in regulatory reporting.