ATO determinations of effective life are made by legislative instrument and published on the ATO Legal Database.
The Primary legislative references are Sections 40-95, 40-100 and 40-105 of the Income Tax Assessment Act 1997.
Effective lives were published in tables attached to taxation rulings relating to the effective life of depreciating assets. Previously, these tables were updated and revised every 6 months by an addendum to Taxation Ruling TR 2000/18. There were several such addendums.
The publication of Taxation Ruling TR 2006/5 saw the practice of periodically updating the tables change to issuing a new ruling. TR 2022/1 Income tax: effective life of depreciating assets is the last such ruling published.