Some 1.8 million ANZ Bank customers across the country were left with limited cash withdrawals and could not access EFTPOS, or accounts over the Internet and in branches due to an internal network problem.
The glitch hit the organisation less than 24 hours after St George suffered a similar outage from an internal systems error that affected its teller systems and online banking early yesterday.
Optus, which provides telecommunications for both banks, said it was not to blame for the incidents.
The network outage, as yet undisclosed by the bank, affected systems between 9am and 10.45am today.
Transactions occurring during both outages were held offline and processed once systems and connectivity were restored.