<p>Tax earmarking, or hypothecation, refers to the assigning of receipts either from a single tax base, or as a proportion from a wider pool of revenue, to a specific end use; it contrasts with general fund financing of expenditure from consolidated receipts. The idea has been seized on both by those who want to defend the public sector who think it would make taxation popular and by those who want to cut public spending who expect the opposite effect. Earmarking may be applied in a strong or substantive sense, or in a weak or nominal sense. In the strong case, revenue determines expenditure, or at least revenue must match expenditure, and there may be associated referendums on the amount of spending and the tax rate. In the weak case, earmarking is purely formal - undertaken to make the system more transparent and to inform the taxpayer of the cost of a service. Earmarking may also be wide, covering a whole spending programme, or narrow, for a specific project within a programme. The principal example of earmarking (nominal) in the UK today is National Insurance contributions (NICs) which go to the National Insurance Fund out of which contributory benefits are paid. This paper considers the range of support for earmarked taxes, examines the issues, and asks if there is a role for such taxes in the British system.</p>