Off-market share buybacks in Australia are often structured with the buyback price comprising a large dividend component (which may carry imputation tax credits) and a small capital component. This unique structure has the consequence that institutions on low tax rates stand to benefit most from selling shares back to the company. In this paper, we explore evidence of abnormal trading activities around key dates in the conduct of off-market buybacks and investigate the drivers of these activities. We find evidence of abnormal trading activities around the initial announcement and the final announcement dates of the buyback. The significant differences in abnormal volumes between the buybacks with and without imputation tax credits highlight the importance of tax motivations in explaining abnormal trading activities in the shares of companies conducting off-market buybacks.