ANZ is asking customers to get in touch if they believe they lost out financially due to the failure of its overhauled internet banking service.
Customers were unable to access their accounts for much of Monday when the internet banking crashed, prompting embarrassment for the bank and angry sprays across its Facebook and Twitter pages.
The bank said services were restored and running normally on Tuesday but that anyone who felt they missed out by being unable to make payments should contact them.
"Our internet banking site experienced some technical issues yesterday and was offline while we worked to fix the issue," an ANZ spokesperson said.
"We would like to apologise for the inconvenience this caused."
Personal banking customers are now on the new system, which the bank had touted as user friendly and more intuitive, but ANZ's 10,000 business customers have been put back on the old interface and will have to wait a bit longer for their upgrade.
The bank began fielding complaints before 9am on Monday, with issues raised including the inability to pay staff or transfer funds to cover rent.
"@ANZ_AU #ANZ_AU ANZ online is still fragile, unreliable, possibly insecure as ever. Don't they test these things?" one angry user wrote, tweeting out a screenshot of the crash.
Service to ANZ's mobile app was swiftly restored but access to the browser-based internet banking was only restored late in the afternoon.
ANZ announced the slow resumption of services at about 5:20pm and extended its deadline for payments past the usual close of business to about 9pm to process outstanding transactions.
It stressed that its goMoney mobile app, ATMs and branches had all been available during the outage.
The root cause is still being investigated but, following its introduction over the weekend, it is possible that the level of demand at the start of the working week was a factor.
One unhappy customer queried whether the end of the month was the right time to initiate such an ambitious overhaul.
