Capital gains tax reforms legislated in Australia’s 2026–27 federal budget will take effect on July 1, 2027, replacing the current 50% CGT discount with cost-base indexation plus a minimum 30% tax on real gains for assets held over 12 months. Gains accumulated before that date keep the existing, more favourable 50% discount treatment — which means a property’s market value on July 1, 2027 becomes the dividing line used to split any eventual gain into a pre-reform and a post-reform portion.
Property investors can rely on the Australian Tax Office’s default fallback calculation, which spreads a property’s total growth evenly across its full ownership period, or commission a professional valuation dated to the transition point. Valuation firm Opteon modelled six sample properties across New South Wales, Victoria and South Australia to compare the two methods, and found the professional valuation produced a better outcome for the owner in five of the six scenarios — particularly for long-held properties with uneven growth, such as a sharp early boom followed by a flatter period, since the ATO’s straight-line formula does not capture uneven timing.
“For most investors, the value of their property as of July 2027 will be one of the most important numbers in their financial life, and it isn’t one to leave to the last minute,” said Opteon managing director Scott Chapman. Suburbanite director and property valuer Anna Porter Primmer added that owners who rely on a formula that doesn’t reflect what actually happened in their local market “could potentially pay thousands, or even tens of thousands, more in tax.”
Investors do not need to have the valuation completed on July 1, 2027 itself — valuers can begin work early and still date the assessment to the transition point, though Chapman noted that a retrospective valuation done well after the date becomes progressively more expensive to reconstruct, potentially costing double what an on-time valuation would.
