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We can confirm that Optus plan to introduce voice challenges on their network as part of their scam prevention measures from 1 July 2025.

From 1 July 2025, Optus plan to start progressively applying an Interactive Voice Response (IVR) Challenge to calls using an Optus Mobile Calling Line Identifier (Optus Mobile CLI) that are originated outside the Optus network. This Interactive Voice Response (IVR) Challenge will be experienced as follows:

  • IVR  – “Welcome, to connect your call please enter the following three digits followed by the hash key xxx.”  (where xxx is a random 3-digit number)
  • Where caller inputs the correct 3-digit number the call will be allowed to progress 
  • Callers are given a total of 3 attempts to input code correctly before call is disconnected

Optus have advised that they do not intend to provide broad support for whitelisting to allow carrier diversity or redundancy. They may allow specific use cases to be whitelisted and cited the example of test numbers for mobile roaming.  If the use case is accepted there will be documentation required, and this may take up to 4 weeks to put in place.

Optus have acknowledged that many of their customers are engaging in multi service practise today where they are using an Optus number - to which they have rights of use - to originate traffic outside of the Optus network.  While this is common market practise today and not prohibited by local Australian regulation, Optus have noted they do not intend to allow this going forward. 

Any customers using Optus Mobile CLI that would like to continue to use the flexibility of multi service practise for supplier diversity and redundancy purposes are encouraged to port their numbers to an alternative carrier.

Optus advised in an earlier notficiation that calls that originate on the Optus network and return to the Optus network via call diversion would not be impacted. They have now confirmed that a SIP diversion header will need to be presented.

Optus have noted they intend to implement further measures in future, including applying the IVR challenge to Optus Fixed numbers, date to be advised