Telstra says it has fixed an issue that prevented people from using EFTPOS and ATMs.
The telco apologised for the disruption, which began on Friday, and thanked people for their patience while they worked to fix it.
"The issue that was impacting some machine to machine data services, including EFTPOS and ATMs, has been resolved," a spokesperson told SBS News.
"The issue in a vendor's network resulted in intermittent authentication of devices which prevented some of them connecting to the network ... All devices should now be capable of connecting."
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Earlier, Telstra had advised people to carry cash instead of relying on 'tap-and-go'.
The outage affected businesses in numerous states on Saturday morning.
Telstra was inundated with angry customers on Twitter.
ANZ has also been forced to apologise to annoyed clients on social media.
Several customers vented their frustration on social media.
The outage comes days after an issue affected access to some Telstra apps and the company's website, including cloud services.
