Hi wombatlawnandgar,
The best report for calculating turnover is a Profit and Loss Comparison report. The GST Turnover relates to the gross business income amount, which in this report would be the Total Income amount - however, there may be additional factors to take into consideration (international sales, personal transactions not related to your business or so on). If you are unsure on the requirements for the turnover or what totals you should be using, the ATO has provided a Turnover Test that will guide you through how to calculate your turnover and determine whether or not you meet their requirements. This guide also includes how to work out the right comparison period and a guide to the modified decline in the turnover test for JobKeeper.
-Kass
