The bank said ATMs and eftpos services were not affected.

The outage affected the Commbank phone app and Netbank online banking system and saw irate customers take to social media to vent their anger.

However, at least two customers said their eftpos was declined. One woman she had to leave her groceries behind after shopping for one hour because she could not pay at the register.

"Was great being stuck at the check out today left red faced. Ran up the street to the local branch and they didn't even know the system was down. Well done commonwealth great work," another customer wrote on the bank's Facebook page.

Another wrote: "My bills are going to cost an extra $90 because they're late. Thanks commbank."

A third wrote: "In a foreign country and unable to access my own funds in order to pay for my hotel and get to the airport. What a joke."

A Flight Centre employee said she had customers desperately needing to book over $10,000 worth of flights, but who could transfer the money.