Book excerpt: This series of technical notes is produced on different topics of a national nutrition information system (NNIS) that are included in the first-ever global guidance on NNIS published in 2021. While the fundamental modules of the guidance describe the basics of a NNIS, each technical note deals with a specific topical area and presents details on those topics. The technical notes will help design and implement a NNIS and/or integrate a nutrition information system in the existing health management information system. A situational assessment of existing system is an essential first step for establishing a national nutrition information system. This technical note provides guidance on a series of key questions related to operational assessments of a national nutrition information system. It also includes two important checklists for assessing an existing national nutrition information system – one on a set of possible investigative questions that could be used in an assessment and the other on a series of key actions for planning and conducting an assessment.