A codebook is a foundational document in qualitative research methodology that lists every code used to categorize data, along with its definition, inclusion criteria, exclusion criteria, and representative examples. Researchers apply a codebook to interview transcripts, open-ended survey responses, and observational notes to ensure that thematic analysis is systematic rather than impressionistic. A well-constructed codebook makes qualitative findings auditable, which is critical when presenting results to senior stakeholders who need to trust the evidence behind the conclusions. In enterprise research contexts, a shared codebook also enables multiple analysts to work on the same dataset without introducing inconsistency, and it creates a reusable framework that can be applied across waves of research or longitudinal brand tracking studies.