International debates about the comparative institutional structures of welfare states have focused on social expenditure and the inclusiveness of social policy. However, these debates have not accounted for the significant rise of fiscal welfare and, in particular, social tax expenditures (STEs) in our understanding of welfare regimes. The growth of STEs has been particularly significant in Australia. While there has been recognition that STEs contribute to a second tier of welfare provision in some policy domains, there has been no systematic attempt to account for them within the institutional structure of the Australian welfare state. In this article, we chart the rise of STEs, the reasons for their growth in the Australian political economy and conceive of them as forming a second institutional layer of a dual welfare state. We conclude by suggesting that this analysis has broader implications for other, particularly liberal, welfare regimes.