A Certified Reference Material (CRM) is essential for ensuring accurate analytical measurements, serving as a benchmark for verification, validation, and calibration of test procedures. In accordance with ISO 17034:2016, a CRM for high ash coal was developed to support quality assessments in the coal industry. This CRM provides precise property values, including ash content, volatile matter, and gross calorific value (GCV). An initial batch of 700 candidate reference material bottles was prepared and stored under controlled conditions (18 °C) to maintain homogeneity and stability. The homogeneity study addressed within-unit and between-unit heterogeneity, with two-way ANOVA analysis confirming no significant variations (p-value > 0.05). Additionally, short-term and long-term stability studies were conducted. An Inter-Laboratory Comparison (ILC) study involving ten laboratories across the country was conducted to assign the property value. After considering the uncertainty associated with homogeneity, stability and the property value assignment, the tentative values are GCV (4213 ± 41 kcal/kg), ash content (40.74 ± 1.93 %) and volatile matter (27.45 ± 3.51 %). This indigenous reference material for high ash Indian coal strengthens coal analysis standards, ensuring enhanced precision and consistency for researchers and industry professionals.