A Methodological Framework for Sample Size Determination in Quality Control of Financial Payment Messaging

This paper presents a structured methodological framework for determining the optimal sample size in the ex-post quality control of financial payment messages (e.g., SWIFT and SEPA). Using the Yamane approximation and Cochran’s sampling theory, the study demonstrates how financial institutions can balance statistical rigor with operational sustainability. The analysis provides a practical lookup table for sample size determination across different population scales and error margins, identifying a convergence point that ensures a 95% confidence level. The proposed approach aims to standardize audit processes, enhancing transparency and regulatory compliance in high-volume transactional environments.