This investigation focuses on the marginal presence of informal language in the L2 curriculum and advocates for its inclusion via translation-related tasks to develop sociolinguistic competence. Research in L2 teaching shows that classroom-based learners often overuse formal registers, tending towards monostylistic communication, which may hinder them in casual, day-to-day interactions with native speakers (Mougeon, Nadasdi and Rehner, 2010). This may also affect the learners’ agency and expression of identity if they feel the language they use is inappropriate in context. The ability to alternate between various styles, registers and discourse markers relates to identity, as it is a means to demonstrate in-group membership (Regan, 1996, 2010). Lasan and Rehner’s (2018) preliminary study also indicates a positive association between an understanding of sociolinguistic variation and the ability to express and perceive identity in the L2. Furthermore, the regular omission of informal registers and slang from the classroom contrasts with their widespread daily use (Mattiello, 2005). Translation tasks can facilitate interaction with an endless number of authentic language samples rooted in various situations and styles, and have been shown to have great didactic potential in the L2 classroom (Bruton, 2007; Laufer and Girsai, 2008). In particular, they can increase awareness of communicative competence and strategies (Pintado Gutiérrez, 2012; Pintado Gutiérrez and Torralba, 2022) and L2 learning (Carreres, 2006, 2014; House, 2008; Carreres and Noriega-Sánchez, 2011; Machida, 2011; González Davies, 2014; González-Davies, 2017, 2020). It has also been argued that translation can help to develop the learner’s L2 style (Schaffner, 1998), although this relationship has yet to be fully investigated. This investigation therefore lies at the intersection of learner agency and the use of informal language in the L2, the role of translation in L2 teaching as a tool to introduce informal language, and the relationship between sociolinguistic competence and identity in the L2.