The article reviews the limited existing social policy literature on taxation and sets out a case for the incorporation of the study of taxation into the accepted remit of social policy. Social policy has historically been concerned with the services and benefits which flow from public expenditure, and people’s experiences of them, rather than with taxation, and the contributions by individual researchers have tended to remain marginal to the main focus of social policy. The article offers a speculative account as to why taxation has remained peripheral to social policy and presents three arguments for the mainstreaming of tax in social policy’s domain of study. These concern the role of taxation in shaping the distribution of resources, a fundamental pre-occupation of social policy; the contribution social policy scholars can make to shaping a new discourse surrounding taxation, foregrounding issues of equity and need; and how social policy’s engagement with taxation can influence the politics of the welfare state.