Tax file numbers of thousands of ANZ customers have been lost after a system upgrade went wrong.
In a letter obtained by iTnews, the bank informed affected customers their data had been deleted in error and was not able to be reinstated due to “legal requirements by which TFN data is maintained”.
The bank subsequently charged customers withholding tax on interest earned on their deposit accounts, which is usually the case for customers that had not supplied their tax file number.
A spokesperson for the bank confirmed the data loss, and said the tax file numbers were deleted from customer profiles during a “routine upgrade to a customer system”.
The issue directly affected around 3000 customers, predominantly those with interest-earning accounts, however data was also lost for some customers without such accounts.
“We are in the process of contacting impacted customers to apologise for the error and asking them to provide their tax file numbers so that we can rectify the error,” the spokesperson said.
The bank was not able to automatically reinstate the data due to requirements on retrieval of tax file numbers under the Income Tax Assessment Act, the spokesperson said.
ANZ is part-way through a $1.5 billion IT transformation program. It chose not to completely overhaul its core banking system, as is underway at the Commonwealth Bank and NAB.
Chief information officer Ann Weatherstone has previously pointed to technology projects being based on an "architected approach" rather than a total core banking replacement.
Last year APRA head of IT risk David Pegrem said there would be “no tolerance” for service outages at Australia’s banks and building societies due to neglected legacy systems.