The outage affected EFTPOS terminals and access to ATMs across the country for "a number of enterprise customers nationally", a Telstra spokesman told AAP.
A spokesperson for Telstra said it was investigating the issue.
Telstra apologised "for any issues caused" said it will provide an update once it knows more.
According to Down Detector, the issues began around 2:30pm AEST and are hampering a bunch of services from Commonwealth Bank, ANZ, Telstra, NAB, Westpac, St George and Xbox. We are continuing to monitor all services as this happens.
Online shopping, ATMs and Eftpos services were affected by a Telstra fault this afternoon and are ongoing.
A Telstra outage is affecting EFTPOS machines and ATMs in parts of the country, leaving some payment methods offline.
Westpac and its subsidiary St George have tweeted that some branches, ATMS and services in Sydney are not working and it is working with external providers to restore services. However, it only appears to be affecting low-value transactions.
Most customer services have now been restored, and we're working with our customers on the remaining few.
- CommBank (@CommBank) July 11, 2019(2/2) We are experiencing higher than normal calls into our call centre. There is no need to call us if you are experiencing problems with these services.
Caltex service stations, Coles and Woolworths stores, Big W and liquor retailers BWS and Dan Murphy's weren't spared from the outage.
"Very rare occurrence for CBA so I'm not going to jump up and down throwing a tantrum like a child on social media because I can't have my way all the time".
Supermarket chain Woolworths said its stores were still trading as they are able to process payments manually, however, when ZDNet walked into its Town Hall store in Sydney, a sign greeted shoppers stating it was trading as cash only. "We're working with the supplier to resolve the issue as quickly as possible, and apologise for the inconvenience", the company wrote on Twitter.