Context. Public procurement is an important economic factor. To protect against corruption government organizations are required to apply principles of non-discrimination and transparency for the procurement of goods such as software and of services such as software development. As a consequence, communicating requirements in software procurement has become challenging from the perspective of fairness and transparency, and also from the perspectives of system value and acceptance. Objectives. This study investigates requirements communication techniques which are being practiced in WTO-regulated tenders. The study also identifies challenges and determines the efficiency, effectiveness, and legal compliances of these techniques Methods. A systematic literature review is used to determine requirements communication approaches used in public procurement projects and the difficulties identified. This is followed by a case study to research the known requirements communication techniques used in the selected case through conducting interviews and artifact analysis. Results. The contributions are guidelines for stakeholders to select suitable techniques to communicate requirements during the procurement process. Challenges and recommendations are presented to be taken into consideration while planning software procurements. Conclusions. This study concluded that from a total of 17 requirements communication techniques, 14 have been used in the project analyzed in the case study. It is also stated by the interviewees that all of the techniques are legal to use in public procurement with the exception of one, and this is Interview. From both the literature review and the case study conducted in this research, balanced communication techniques are concluded to be most recommended since they will lead to more interaction between customers and suppliers to communicate requirements.