The Common Assessment Framework (CAF) is an electronic system for assessing children and sharing information between child welfare professionals, which is at various stages of pilot and implementation in England and Wales. Research by the authors in England (Peckover et al., 2008a, 2008b; White et al., 2008) and Wales (Pithouse et al., 2004; Pithouse, 2006) informs this paper in order to compare CAF as implicating a number of policy 'goods', with CAF as a set of worker and organizational accomplishments. Our interest here is that in the course of implementation, policy aims have become submerged in day- to- day practice and that, analytically, there are differences between the 'CAF of policy' and the 'CAF of practice'; in brief, there are, conceptually, two CAFs, the formal construct of policy and the applied CAF as constructed by multiple organizations across Wales and England, wherein there is no singular model. Indeed, we demonstrate that there are all manner of common assessment designs operating in the world of practice. Rather than rehearsing our research findings (the above sources offer an abundance), we use this opportunity to develop and synthesize our arguments about key assumptions and conceptual properties that underpin the CAF of policy and practice, and which may have wider provenance in respect of information and communication technologies (ICTs) in child welfare.