A research project that aimed to trial and evaluate a prototype diagnostic tool for assessing VAT/GST compliance costs, conducted under the auspices of the University of New South Wales Business School in Australia and with the co-operation of academic and other similar bodies in thirteen countries representing a mix of advanced and developing economies from all continents (Australia, Belgium, Canada, Chile, Croatia, Ethiopia, Greece, Indonesia, New Zealand, Malaysia, South Africa, United Kingdom, and Vietnam). The findings appear broadly aligned with researchers’ and tax authorities’ expectations of the merits of a prototype diagnostic tool for gauging the nature and likely overall incidence of VAT compliance costs at the country level, and its use in comparative cross-country assessments. There appear to be opportunities for quite a few countries to bring a stronger emphasis to compliance burden management, and to enjoy the additional benefits that can result from such efforts. Subject to the additional funding prospects, the intention for the future is to test the tool across a broader cross-section of countries and to explore the potential of a similar “diagnostic” approach for a number of other major taxes, e.g. profit and income tax.