A common task in encounters with professionals is to identify a matter warranting professional assistance. Co-producing a 'social workable' matter in social work encounters as an interactional achievement is yet to be explored. Specifying this as an institutional and interactional project creates the opportunity to analyse how topics are collaboratively used in social work encounters to achieve a joint understanding of the work for the session. Such projects offer insights into the social actions involved in identifying matters that are relevant to the service, setting and professional encounter. Conversation analysis (CA) of real-world social work sessions offers a way to understand how social workers and clients produce, elaborate and pursue topics as a collaborative achievement. This detailed analytic approach illuminates how social workable matters are co-produced in interaction and creates an opportunity to examine and improve collaboration in interpersonal practice contexts.