Online services are being restored following a widespread outage that affected ANZ, Westpac and the Commonwealth Bank, as well as other businesses such as Virgin Australia and Australia Post.
On Thursday afternoon, customers took to social media to report troubles accessing bank services online or through banking apps.
NAB was the only one of the big four banks not to experience any disruption, along with many of the smaller banks and credit unions.
However, the problems went far deeper, with staff at some of the major banks unable to access the internet and the Reserve Bank's website and other systems also down for a period of time.
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