Reconciliation is a critical governance control in mining operations, providing transparency over the relationship between planned and actual performance across the resource, reserve, mining, and processing value chain. The F-series factors, originally proposed by Parker (2012), are widely used to assess the accuracy of mine planning and execution by comparing reserve, production, and plant outcomes. Building on this framework, the R-series factors (Hargreaves et al, 2022) extend reconciliation upstream by tracking how modifying factors such as dilution, ore loss, and information effects are applied from the resource model through to production. While these frameworks are increasingly being adopted, their application in underground mining remains challenging. Selective extraction, irregular geometries, limited visibility, and inconsistent depletion definitions frequently result in spatial misalignment between models, leading to reconciliation outcomes that are difficult to interpret and, in some cases, misleading. Without a consistent depletion basis, apparent variances may reflect differences in reporting volumes rather than true geological or operational performance. This paper presents a standardised approach to underground reconciliation based on a ‘common volume’ depletion methodology. The common volume represents the unified spatial extent of material mined or sterilised during a reporting period and can be applied consistently across resource, reserve, grade control, design, and production models. This approach enables spatially valid calculation of F- and R-series factors and ensures that reconciliation results reflect genuine modifying factors and execution outcomes rather than artefacts of inconsistent geometry. The methodology is demonstrated through a case study from Newmont’s Tanami underground gold operation. The results show how integrating F- and R-series factors within a common spatial temporal framework improves insight into dilution, ore loss, and information effects, supports calibration of planning assumptions, and strengthens confidence in reconciliation performance. The approach is framed within the evolving industry context, including proposed updates to the JORC Code, reinforcing the role of reconciliation as a foundation for transparent, defensible reporting in underground mining operations.