As a highly frequent discourse marker in spoken English, "so" prototypically indexes a ‘resultative’ or ‘inferential’ relation between two propositions. This article, however, focuses on instances of "so" that do not overtly preface a proposition, but occur either at the end of an intonation unit or as intonation units in themselves. It is argued that non-prefatory tokens of "so" can prompt the interlocutor to recover an implicit proposition and establish the relevance of the prior segment to the turn, or can merely serve as a turn-yielding device. This article lays bare these non-prefatory uses of "so", as well as the four discourse structures in which they operate, in a corpus of English interviews with native speakers of English and Dutch, enabling the comparison of native and learner data. Contrary to previous studies of discourse markers, and of "so" in particular, (the non-prefatory use of) "so" is found to be significantly more frequent in the learners’ speech than in the native speakers’. This is attributed to an interplay of three main factors: the learners’ desire to be viewed as coherent speakers, their limited inventory of markers and a functional resemblance of so with comparable markers in the learners’ mother tongue.