This study examined the effect of electronic tax systems on internal revenue generation in Kogi State, Nigeria. The motivation for the study arises from the need to enhance internally generated revenue in the face of declining federal allocations and inefficiencies associated with manual tax administration. Specifically, the study investigated the effect of e-filing, evaluated the effect of e-payment, and analysed the effect of e-registration systems on internal revenue generation. The study adopted a survey research design, utilizing primary data collected through structured questionnaires administered to staff of the Kogi State Internal Revenue Service (KGIRS). A total of 120 questionnaires were distributed, out of which 105 were validly completed and used for analysis. The data were analysed using descriptive statistics, correlation analysis, and multiple regression techniques. Findings revealed that electronic tax systems have a positive and significant effect on internal revenue generation in Kogi State. Specifically, the results showed that e-filing has the strongest and most significant effect, followed by e-payment, while e-registration has a positive but relatively weaker effect. The study concludes that the adoption of electronic tax systems enhances efficiency, reduces revenue leakages, and improves tax compliance, thereby increasing internally generated revenue. It recommends strengthening ICT infrastructure, improving taxpayer awareness, enhancing system integration, and providing continuous training for tax officials. The study contributes to existing literature by providing empirical evidence on the role of digital tax systems at the sub-national level in Nigeria.