A $3.7 million smack on the wrist.
Westpac will pay that fine in compensation to more than 19,000 customers, after admitting to breaching consumer finance law.
The bank failed to provide key information to credit card customers before they entered into contracts.
The issue affected new credit card customers who received their card without receiving a welcome letter containing disclosure information between May 2017 and March 2018.
Westpac reported the issue to the Commerce Commission in March 2018, who filed High Court proceedings against the bank in July last year.
Massey University banking expert Claire Matthews says the bank will definitely be more cautious from now on.
"It's bad enough if something ahs gone wrong, but if you can put your hand up and say 'we've found this problem, we're sorry, let's fix it', that's much better than someone else finding out on your behalf."