Domestic workers who live in private households often lack access to decent work and labour rights. Formalization is widely understood as a normative strategy to improve working conditions. In Germany, the debate surrounding domestic live-in work has centred on “legal certainty” and this article discusses whether and how legal certainty could contribute to formalization. Legal developments (for example, in Austria) show that legal certainty can actually have the opposite effect, by disguising bogus self-employment more effectively. I argue that, similarly, not all claims to establish more legal certainty are likely to improve the situation of live-in care workers in Germany.