This paper examines how social categories can be treated as an interactional discursive resource in order to accomplish a specific social action. Traditional studies have treated social categories as matters of cognitive perceptual reality. However discursive research has criticised this approach preferring to view them as matters of description in overt talk. Therefore we make use of discursive psychology, applying it to the specific social action of complaining in order to analyse how the construction of social categories can increase the persuasive nature of a complaint. Furthermore we utilise the internet as a relatively unexplored rich source of data for the study of discourse and social practice analysing complaints identified in comments posted in online news forums. We show how commentators make use of social categories to increase the persuasive nature of their complaints in three main ways namely: the construction of social categories through contrast formulations, using the relevance of one social category to excuse a complaint regarding another category and the use of personal identity. The analysis highlights the fact that social categories only make sense as part of an interactional context and furthermore are reflective of the intentions of complainers. Commentators considered both the context of the complaint and their subjective investment in it when using social categories. Furthermore our study is the first ever discursive complaints study conducted using the internet leading us to identify similarities between complaints online and in other contexts.