This paper examines the contribution of behavioral economics to tax reform by examining two major reforms in the United Kingdom which may be seen as natural experiments – the reform of local taxation and the introduction of value added tax. The case for both was based strongly on mainstream economic analysis but one was a failure and the other a success. The introduction of the local community charge, or ‘poll tax’ as it became known, was such a failure that not only did it have to be repealed but it was also a factor in the downfall of Mrs. Margaret Thatcher as Prime Minister. The introduction of value added tax took more account of behavioral factors and was successful. The paper concludes that a wider approach based on behavioral as well as mainstream economics may have considerable advantages in developing tax policy.