Traditional food MSMEs play a vital role in supporting the local economy, yet they still face numerous challenges in financial management, particularly in recording production costs and determining business profits. The Lanting Bu Yah Khas Purworejo Traditional Snack Shop MSME is a home-based business that still uses a simple manual recording system, resulting in the calculation of Cost of Goods Sold (COGS) not fully incorporating all production cost components. This situation has the potential to lead to inaccurate net profit information and errors in business decision-making. This study aims to evaluate the COGS calculation and analyze the accuracy of net profit at the Lanting Bu Yah Khas Purworejo Traditional Snack Shop MSME using the full costing method. This study employed a qualitative approach with a case study approach. Data were obtained through observation, in-depth interviews, and documentation in the form of transaction records, purchase receipts, and production process data. The analysis was conducted by comparing the production cost calculations applied by the MSME with the results of reconstructions using the full costing method, which includes raw material costs, direct labor costs, and production overhead costs. The results indicate significant differences between the MSME's COGS calculations and the full costing method. The COGS (Cost of Goods Sold) based on MSME records is Rp10,398 per kilogram, while the full costing calculation results in Rp17,912 per kilogram. This difference results in the MSME's calculated net profit of Rp7,552,000 per month differing significantly from the actual net profit based on full costing, which is only Rp38,333 per month. The research concludes that the manual recording system implemented by the Lanting Bu Yah MSME is unable to provide accurate cost and profit information because it still ignores several production cost components. Implementing the full costing method can provide a more realistic picture of the business's financial condition, thus assisting MSMEs in determining selling prices, controlling costs, and maintaining business continuity.