Since 25 November the bank has been plagued by payment processing problems that were initially attributed to a "corrupted file in the processing batch".
According to The Australian newspaper, today saw customers in Melbourne unable to withdraw cash from ATMs while others were unable to access their accounts online and some noted balance inaccuracies.
In an updated statement on its Web site, the bank says: "NAB can confirm that the majority of customer payments and transactions have been completed and most account balances are now up-to-date. We know that some customers are still experiencing inconsistencies and we're actively working to address these as soon as possible."
With over 6,000 customers understood to have lodged compensation claims over the outages, NAB has called in KPMG to investigate. According to the Herald Sun, Christmas parties have been postponed until the New Year as staff struggle to deal with the fall out.