This paper is positioned at the interface of second/foreign language (L2) assessment and Conversation Analysis-Second Language Acquisition (CA-SLA). It explores challenges of ratability in assessing interactional competence (IC) from three dimensions: an overview of the conceptual and terminological convergence/divergence in the CA-SLA and L2 assessment literature, a micro-analytic Conversation Analysis of test-taker interactions, and the operationalisation of IC construct features in rating scales across assessment contexts. It draws insights from these dimensions into a discussion of the nature of the IC construct and the challenges of IC ratability, and concludes with suggestions on ways in which insights from CA research can contribute to addressing these issues.