For many taxpayers the uncertainty inherent in the tax system makes paying taxes akin to a game of chance. Some people gamble on the ambiguity of the law and intentionally under-report their earnings, whilst at the other end of the spectrum, others overcompensate for any possible misdemeanours and pay more than they owe. There is great variety of taxpayer behaviour patterns in between these extremes. Existing theories have failed to clarify the complexities of taxpayer decision making and thus failed to establish a useful platform for agencies to influence and encourage voluntary compliance. This study investigated the factors influencing business tax payers' decision on whether to report income and deductions correctly in their 2011 income tax return. The proposed model based on Ajzen and Fishbein's reasoned action approach (the Theory of Planned Behaviour -TPB) has genuine applicability in the tax compliance context. The research was conducted in two phases. Firstly, an online pilot survey was used to elicit salient beliefs in order to construct the primary (TPB) questionnaire. The resulting online survey was distributed to taxpayers who were asked to identify whether, in the previous 12 months they had (i) self-initiated contact or received assistance from the Tax Office; (ii) been contacted via an audit or other verification scenario; or (iii) had no personal contact with the Tax Office. The aim was to determine whether the TPB can reliably predict taxpayers' intention to fulfil their tax obligations and if so, whether it can be used to develop intervention strategies to improve voluntary compliance. The results show that intention to comply is not always a strong predictor of compliance behaviour. The majority of taxpayers who wanted to comply, failed. As complexity and difficulty in performance increases, additional factors are required to predict compliance, such as awareness of the rules. Complexity also reduces the predictability of behaviour. Behaviour prediction can be enhanced by quantifying environmental complexity, providing performance support, and eliminating potential obstacles. Intention can only be leveraged for compliance strategies when the tax system creates the optimal environment for taxpayers to successfully comply. The paper reports the findings and discusses their theoretical and practical implications. The results have significant implications for both behaviour prediction and tax compliance strategy development. The study has broad generalisability as it provides a new model for government agencies to assist them to understand and engage effectively with the people they serve. © School of Taxation and Business Law (Atax), Australian School of Business The University of New South Wales.