This paper examines whether the specific design of information and communication technology (ICT) implementation plays a critical role in enhancing the fiscal efficiency of local governments. Although ICT has been widely promoted through e-government initiatives to improve government operations, the effectiveness of implementation specifications has received limited attention. We study Japan’s Regional Information Platform (RIP), a standardized system specification that facilitates interoperability across municipal administrative systems and weakens vendor lock-in. Building on a model of municipal procurement under switching costs, we show that standardization reduces expenditure through two channels: weakened vendor lock-in that lowers system costs, and improved cross-departmental interoperability that reduces labor input. Using variation in RIP adoption across Japanese municipalities, we estimate difference-indifferences models and find that RIP adoption substantially reduces per capita total expenditure. The decline is also driven by decreasing system-related and persone expenditure. These findings suggest that e-government outcomes depend not only on ICT adoption itself but also on implementation design.