The modernization of the National Tax and Customs Administration's (NAV) 20-year-old data warehouse was a complex and critical project that impacted the foundations of the institution's IT systems. The aim was to create an integrated and efficient system that meets the needs of a modern tax authority. Over the 2.5-year process, more than 100 experts worked on the project's success while ensuring the uninterrupted operation of NAV's daily services.