The main justification used for the reduction in the top rate of income tax from 50% to 45% (effective from April 2013) in George Osborne’s Budget yesterday was an analysis by HMRC, published on the same day, which claimed that the top rate was raising very little money – less than £1 billion on an annual basis, rather than the £2.7 billion projected in the March 2010 Budget. In this blogpost I assess the evidence presented by HMRC in support of this claim. Based on the HMRC research as well as other recent evidence on the revenue impact of increases in top tax rates, I reach two conclusions:
(1) the methods used by HMRC to assess the yield from the top rate are likely to produce an underestimate of the revenue-raising potential of the 50p rate in the tax system as it currently stands;
(2) even if the HMRC estimate is correct, for the most part it reflects easily correctible anomalies in the tax system which allow a large proportion of high income individuals to avoid paying 50% tax relatively easily. Reforming the system to close these loopholes would ensure that the 50p rate raises substantially more revenue than it does now.

