A technology glitch is being blamed for MasterCard credit and debit payments made on December 23 and 24 not going through properly.
The bank confirmed the affected transactions had been put through on Thursday night.
Furious Westpac customers have reported being suddenly left hundreds of dollars in overdraft, some saying they have barely enough money to pay for groceries.
Many say they will take months to get back in the black and it's been a dreadful way to start 2023.
One customer said they were now nearly $810 overdrawn.
“I don’t know how to pay for food, as whatever funds coming in will be soaked up by this $800. An apology is not going to put food on the table for our four children.”
One single mother on a benefit told The New Zealand Herald she discovered her account unexpectedly overdrawn by $133.
”My family will suffer for the remainder of the school holidays,” she said.
A grandmother raising her 10-year-old grandson said she was off to buy school supplies today but instead woke to discover she was $327 in debt.
“Can’t see through my tears to write in detail how I feel about this. Have no idea how I am going to catch up to see a positive balance back in my account,” she told the Herald.
In a post on its Facebook page, Westpac said all affected payments should now be showing and any overdraft fees and interest incurred as a result of the mistake would be automatically waived.
“Due to a technology issue, some MasterCard credit and debit card payments made on December 23rd/24th were not processed correctly.
“Affected payments were processed last night and should now be visible in accounts. We apologise for any confusion.”
Westpac said it was unable to address specific questions today surrounding a lack of communication between the bank and customers and claims bank accounts were not reconciling with holiday purchases.
In the meantime, scores of customers have taken to social media to vent their frustration.
One woman said she had been left in overdraft which threatened to affect her ability to pay upcoming automatic bill payments.
“Not good enough. Xmas/New Years is hard enough due to payment day changes and now this. Should have given us warning when it happened not days later,” she posted.
“Very frustrating Westpac. I’m so careful with my money and just woken to missing money! Single mother here and now don’t have funds for groceries, and as I saw that money had been taken out on those dates!” said another.
“Woke up to $400 in OD,” a third customer said.
One man's transactions didn't add up: “Even though those “missing” transactions were actually showing on those days suddenly days’ worth of transactions are missing from people’s account statements,” Ken Fuse told the Herald.
