In dealing with over-indebtedness and poverty, numeracy appears necessary for affected persons, in order to use the scarce money available with foresight and to avoid financially negative decisions. However, numeracy as an essential part of (financial) basic education for adults has not yet been systematically taken into account in German debt counselling. Nor are the difficult conditions concerning over-indebted life situations considered sufficiently in theoretical models of numeracy or financial literacy. There is a lack of knowledge in adult mathematics education about the mathematical requirements in the context of over-indebtedness and the numeracy practices of persons affected. In this paper we therefore intend to clarify the understanding and significance of numeracy practices in over-indebted life situations from the perspective of German debt-counselling professionals. The empirical basis comprises qualitative data of two group interviews with debt-counselling professionals (n = 11). Amongst other things, our findings show the complexity of contextual factors in mathematical demands and numeracy practices in precarious living situations, which can help to develop current thinking on numeracy and financial literacy.