The study examined the utilization of the Electronic Fiscal Receipting and Invoicing Solution (EFRIS) and its effects on the financial performance and operational efficiency of small and medium-sized enterprises (SMEs) in Kampala, Uganda. A cross-sectional survey was conducted among 320 SMEs across the five divisions of Kampala, collecting data on EFRIS awareness, adoption, and usage, as well as indicators of financial performance and operational efficiency. Descriptive statistics, ANOVA, and regression analyses were employed to analyze the data. The findings revealed that SMEs with higher levels of EFRIS utilization demonstrated improved financial control, more accurate reporting, reduced record-keeping errors, and faster transaction processing, streamlined workflows, and reduced operational errors. Regression results further confirmed that EFRIS utilization significantly predicted both financial performance and operational efficiency. The study concludes that EFRIS functions not only as a tax compliance tool but also as a performance-enhancing system that supports SME growth and sustainability. Based on the findings, the study recommends strengthening user training, improving system integration and reliability, and promoting full adoption of EFRIS among SMEs to maximize its benefits.