The document is intended to inform the public about the results of the study on the assessment of the size of tax gaps and their influencing factors in the construction sector. The document consists of several chapters, which describe the research methodology, the data available for the study, their content and quality, as well as the results achieved and their interpretation in the context of the construction sub-sectors examined. The document concludes with general conclusions on the results obtained and the course of the study, which allows for a decision to be made on the further use of the research results.