This Decision sets out revised, detailed rules for Tax Groups effective for tax periods starting on or after 1 January 2025. It clarifies conditions for forming, joining, and maintaining a group, including ownership and residency criteria. A key provision mandates the application of the arm's length principle to calculate a member's attributable income in specific scenarios, such as when the group utilizes that member's pre-grouping tax losses or pre-grouping net interest expenditure. It also addresses business restructuring within the group (Article 10) and notification requirements, repealing Decision No. 125 of 2023.