Public sector organizations suffer from high levels of technical debt (TD). TD leaves digital infrastructures in a derelict state, making digital transformations costly and risky. Though there is growing research about TD, most studies focus on private businesses. In this study, we conduct a case study examining the TD in a Swedish municipality, analyzing archival data such as project reports, municipality blog posts on digital transformation, and goals to improve citizen experience. We focus on four information systems that support permit application processes. Analysis results reveal the common TD types, consequences, and possible causes. Departments work in silos, case managers’ perspective is prevalent in requirements, while citizens only have a passive role as system users. These lead to various types of TD and high costs when integrating legacy systems into a coherent IT architecture. By diving deep into the data from a digitalization forerunner municipality, we identify TD in the municipality sector and increase understanding of how TD influences digital transformation. Results give a stable ground for further research and practice on mitigating the debt.