The effective operation of any taxing regime depends ultimately upon the revenue authority being able to obtain timely and reliable information about a taxpayer’s relevant activities (both domestically and, increasingly offshore). The most detailed substantive provisions, whether they be income tax, GST, or other regimes, are of little use unless the authorities can obtain the information needed to establish (or at least approximate) a taxpayer’s liability.At a time when revenue authorities are making increasing use of technology in order to assess risk and base assessments, their access powers (or at least the threat of them) remain a key element in obtaining relevant information on which to base assessments. From the taxpayers’ perspective, the erosion of their “supposed long-established right to have their information and affairs kept confidential and private”, in part due to developments in technology and data sharing, means it is even more important to ensure that the access powers whereby such information is collected are on the one hand robust, but on the other hand provide adequate safeguards for taxpayers. It is therefore both interesting and informative to compare and contrast the powers given to authorities in different countries, in order to evaluate them and identify particular aspects of one country’s access powers which might usefully be adopted or refined by others in order to improve their own provisions. A multiple unit case study approach has accordingly been adopted in this paper to compare the access powers available to the Australian Tax Office, New Zealand (NZ) Inland Revenue and Her Majesty’s Revenue and Customs (HMRC) in the United Kingdom (UK).