A Telstra spokesperson confirmed the issue affected "a number of enterprise customers nationally".
The outage is affecting national retailers such as Woolworths, which is unable to process EFTPOS payments at many of its stores.
Whilst the CommBank app and NetBank are still working, CBA ATMs and CBA EFTPOS terminals have well and truly carked it.
An ANZ spokesperson has confirmed it is also experiencing outages, suggesting the problem might be "telco-related", while a NAB spokesperson confirmed "sporadic outages" relating to Eftpos but not ATM services in New South Wales and Queensland.
"We're sorry for any issues caused and will provide an update when we know more", he added.
"The cause of the problem is under urgent investigation and we are working to have full services restored as a matter of priority".
"We're aware of a Telstra network issue impacting electronic payments in our stores", the spokesperson said.
The latest problem comes just weeks after the Reserve Bank of Australia revealed that outages had soared by 40 percent and warned banks and telcos about the dangers of ageing infrastructure. We are continuing to monitor all services as this happens.
The supermarket giant says a Telstra network issue means its stores are having to process payments manually.
CommBank is also advising not to call if you are now having issues.
"Most customer services have now been restored, and we're working with our customers on the remaining few".
"We're sorry if this impacts you".
"We apologise to our customers affected by this". She added that the bank's call-centre is experiencing a "higher than normal" call volume and said there is no need for retail or business customers to call the bank. "Rest assured we are urgently looking into this and will have further updates soon".
ANZ is yet to publish a dedicate tweet, though it has responded to customers experiencing issues.
"At this stage we haven't received any updates from our Merchant Servicing team confirming if there is an issue", a company spokesperson wrote on Twitter.