Humpty dumpty's guide to tax law: Rules, principles and certainty in taxation

Tax systems are, most commonly, rules-based. This gives the impression of techno-rationality in the interpretation of the numbers from which tax bills are derived. In fact, uncertainty and complexity in tax rules are seen as promoting tax avoidance behaviour, as avoiders exploit this complexity. Some authors have advocated that this can be combated by replacing rules-based tax legislation with principles-based legislation, giving tax authorities and the courts the power to interpret legislation purposively. This paper demonstrates by reference to a number of UK tax cases that rules-based legislation already embodies the hidden operation of state power as judges have considerable discretion in the interpretation of rules. The paper goes on to argue that principles-based legislation would further empower the state vis-à-vis the citizen. While this might be intuitively appealing to the vast majority of taxpayers not engaged in tax avoidance, it brings with it the hidden danger of a fundamental alteration of the balance of power between the state and all citizens, and should therefore be treated with caution.