This paper evaluates the permanent and temporary differences between accounting profits and taxable income of South African companies using the data in the SARS-NT panel. It contributes to the establishment of a body of knowledge about book-tax differences of South African companies. Unlike previous research conducted on this topic in other countries, the characteristics of the whole population of South African companies are considered. The results describe the book-tax differences and evaluate the nature and trends in the creation or reversal of temporary differences in South Africa. Significant amounts of book-tax differences were merely described as ‘Other’ in the information that taxpayers submitted to the SARS, which hampers a user’s ability to interpret or use this information sensibly. We further observed that the SARS-NT panel did not contain sufficient information to describe book-tax differences and trends therein by industry. These findings suggest that these are areas to consider to improve the design of tax returns and the development of the SARS-NT panel that will benefit future research.