Until 2026 there was no requirement for mandatory pre-merger notification in Australia. Parties to mergers which may have raised competition concerns were nevertheless encouraged to apply to notify the ACCC for 'informal clearance'; an indication of whether the ACCC will oppose the merger, not oppose the merger, or not oppose subject to conditions.

Most notified mergers were 'low risk' and reviewed during an initial 2-4 week pre-assessment phase without public review. If a review was necessary the ACCC commenced a public review and undertook market inquiries. Usually between 6-12 after pre-assessment phase 1 concluded and the ACCC either issued a final decision or issues a 'Statement of Issues' (SOI) and proceeded to phase 2, including public consultation on the SOI. Phase 2 typically lasted between 6-12 weeks from the issue of the SOI, but sometimes took longer and timelines could be suspended where further information was sought from the merging parties.

Parties could offer merger remedies at any point during the review process; the ACCC did not have the power to impose merger remedies, but could indicate that it would oppose a merger absent undertakings necessary to address competition concerns.

The process was supported by Informal Merger Process Guidelines.

Since 1 January 2026 a mandatory pre-merger notification regime has operated in Australia.