The focus of this publication is on the activities required to demonstrate the suitability of commercial off the shelf (COTS) digital instrumentation and control equipment for use in nuclear safety applications. The publication provides a detailed discussion of the typical challenges associated with the use of COTS devices, including issues associated with unique vulnerabilities and features of digital products. It outlines the strategy for digital COTS device assessment and qualification and describes the typical elements of the process. The publication addresses the specific steps of any justification, including identifying the requirements, selection of the supplier and candidate equipment, planning, assessment and identification of equipment life issues, suitability evaluation and all associated documentation. Guidance on maintaining the compliance of COTS devices as well as related regulatory aspects are also covered.