<![CDATA[Cassava farming is one of the agricultural sectors with the potential to improve community income in West Dumai District, Dumai City. However, most farmers still face challenges in managing production costs because they have not implemented a systematic financial recording system and calculation of Cost of Production (COP). This condition makes it difficult for farmers to determine selling prices based on actual production costs, resulting in inaccurate profit calculations. This community service program aimed to improve farmers' knowledge and skills in calculating Cost of Production (COP) as a basis for determining the selling price of harvested products. The method used was Participatory Action, which included preparation, observation, socialization, training, mentoring, COP calculation practice, distribution of mentoring modules, and evaluation. The results showed that farmers were able to identify production cost components, classify fixed and variable costs, prepare simple production cost records, and calculate Cost of Production based on their farming conditions. In addition, farmers began to understand the importance of cost information as a basis for determining selling prices and evaluating business efficiency. The distribution of mentoring modules also supported program sustainability by providing practical guidelines for farmers to independently implement cost recording and COP calculation. Overall, the mentoring program had a positive impact on improving farmers' managerial capacity, strengthening business decision-making abilities, and supporting more efficient, professional, and sustainable farm management.]]>
