For many property owners valuations will be required to support cost base apportionment and establish CGT positions under the new framework. Where gains straddle the 1 July 2027 transition date, the split between old-rules gains and new-rules gains will need to be defensible. A credible, independently prepared market value assessment at the relevant date is the most reliable way to do that. Valuations must reflect objective market value and be evidence-based, the ATO's existing standards on this haven't changed.