Australia relies on the Collins class submarines as a core element of its maritime defence capability. As the fleet ages, a Life of Type Extension (LOTE) is required to maintain submarine capability and availability until Australia transitions to a future nuclear‑powered submarine fleet under AUKUS. Without a service life extension, these submarines would be withdrawn from service between 2026 and 2036. 

This audit provides independent assurance to Parliament on the effectiveness of the Department of Defence’s (Defence) planning and implementation of the LOTE project to date. There were five recommendations to the Defence aimed at improving project planning, risk management and the quality of advice provided to government. Defence agreed to all five recommendations.

Key points

• The audit found planning and implementation of the Collins class Life of Type Extension project was partly effective.
• The LOTE project involves significant public expenditure. It is critical to avoiding a submarine capability gap during the transition to nuclear‑powered submarines under the AUKUS partnership.
• Since the system and detailed design contract was awarded in February 2022, it has been varied 53 times, increasing by $688 million to more than five times its original value.
• Four of the five key design reviews were not achieved as scheduled.
• In May 2026, Defence proposed and government agreed, a revised service life extension strategy.