This article describes, discusses and presents information about tax expenditure and its relation to social policy. It stresses that the hidden welfare state strongly influences social policy and that only looking at the direct provision of welfare goods may be misleading when making comparisons between countries. The article presents new figures on tax expenditure in relation to social policy and does so in a comparative perspective. It is argued that tax expenditure seems to have an upside down effect, but further research is needed to substantiate this. It concludes that tax expenditure strongly influences the provision, financing and delivery of social policy, and tax expenditure therefore has to be more fully integrated into the analysis of the welfare state.