There is a widespread view that tax systems are too complex and that simplification would be desirable. Complexity leads to cost, uncertainty, avoidance opportunities and the inability to engage in tax issues. And there is a point at which complexity becomes so great and unmanageable that it begins to undermine the rule of law, because it does not enable individuals to regulate their affairs properly. This research project acknowledges that complexity is undesirable but argues that it is to some extent inevitable: complexity should be reduced wherever possible, but simplification cannot be the only, or even the main, driver of tax reform. Where simplicity cannot be achieved consistently with other objectives, there should be institutional mechanisms in place to help taxpayers and revenue authorities to navigate through the remaining intricacies. Improved institutions could assist in managing uncertainty and increasing understanding, as well as leading to improvements in the tax system. In the UK, there is a proliferation of institutional approaches and the relevant institutions do not play the part they could do in improving tax law. In particular, the Office of Tax Simplification (OTS) was created specifically to tackle the issue of complexity, but new institutions need to tackle the problems at root, which the OTS has not been able to do. The announcement by the Chancellor in the summer budget 2015 that the OTS will be put on a stronger, statutory footing in the Finance Act 2016 is recognition of the need for institutional reform, but indications to date suggest that the proposed changes do not go far enough. There is a need for wider institutional reform in the UK; we propose that the Office of Tax Simplification is transformed into a well-resourced Office of Tax Policy, with wider scope than simplification and answerable to a Joint Committee of Parliament on Taxation Policy.