The Australian Communications and Media Authority has started Federal Court proceedings against Optus Mobile over the September 2025 outage that stopped Triple Zero calls connecting across four states and territories. The regulator announced the action on Thursday and alleges 1,005 separate contraventions.

Of the 605 Triple Zero calls made on the Optus network during the outage, 455 did not connect. That is about three in four. The outage began on 18 September 2025 and ran for more than 13 hours, affecting customers in New South Wales, South Australia, Western Australia and the Northern Territory. Ordinary calls went through.

The ACMA alleges Optus Mobile breached two obligations on 1,005 occasions: that it failed to give people making emergency calls access to the emergency call service, and that it failed to ensure those calls were carried to the relevant termination point. The regulator is seeking penalties of up to $250,000 for each contravention. That puts the theoretical maximum at about $251 million.

“Australians rightly expect that when they call Triple Zero, their call will connect," the ACMA chair, Nerida O'Loughlin, said.”

Deaths were linked to the outage in the weeks that followed, and the number has been contested. Optus said police had advised it that two fatalities were connected to the Triple Zero failure, after earlier reporting had put the figure higher. The ACMA's claim concerns the call failures themselves and does not seek findings about the deaths.

This is the second time the same obligation has been enforced against the same company. Singtel Optus subsidiaries, Optus Mobile among them, paid more than $12 million in infringement notice penalties over a November 2023 outage that also cut emergency calls. Those penalties did not prevent the 2025 failure, which came ten months later and ran longer.

An independent review of the September outage by Kerry Schott was released in December 2025 and reported gaps in the company's urgent escalation protocols.

Optus Mobile is a subsidiary of Singtel Optus, which is owned by Singapore Telecommunications. The obligation the ACMA is enforcing sits on the licensed carrier, not on the parent.

Emergency call carriage is not a service a customer can shop for. A person dialling Triple Zero does not choose which network carries the call and cannot switch mid-emergency. Carriage is a condition attached to the licence to run a mobile network, and financial penalty is the only mechanism a regulator has to price the failure of it.

The difference between the two rounds of enforcement matters. The 2023 penalties were paid as infringement notices, which require no admission and produce no court finding. This action asks the Federal Court to rule on whether the law was broken, and that answer goes on the public record either way.

The matter is now before the Federal Court, which will decide whether the contraventions occurred and what penalty applies.