The Information Commissioner's Office (ICO) has served the Bank of Scotland with a fine of £75,000 after customers' account details were repeatedly faxed to the wrong recipients.
Customer information sent out included payslips, bank statements, account details and mortgage applications, along with customers' names, addresses and contact details.
The documents were faxed over a three year period, with the first incident reported to the bank in February 2009 by a third party organisation.
At least 21 documents were faxed to the unnamed third party organisation during this time, with another member of the public receiving a further 10 misdirected faxes.
Both parties had fax numbers there were one digit outside the intended recipient, which was a department within the bank that routinely uploads documents onto the bank's system.
Bank of Scotland was informed of the error on numerous occasions, but continued to make the same mistake. The ICO was eventually made aware of the matter by the third party organisation.
A spokesperson for the bank said: "The security of our customers' data is always our key priority. We apologise that, due to human error, a very small number of documents relating to 32 customers were unfortunately misdirected. This occurred over a period in which several million customer documents, using the same process, were correctly received.
"No customer suffered any harm or detriment as a result of this error. We are continually reviewing our processes to ensure our customers' information remains safe".
The Bank continued to send faxes containing customer details in error, even once the ICO had begun investigating the breaches.
Stephen Eckersley, Head of Enforcement at the ICO said: "The Bank of Scotland has continually failed to address the problems raised over its insecure use of fax machines. To send a person's financial records to the wrong fax number once is careless. To do so continually over a three year period, despite being aware of the problem, is unforgiveable and in clear breach of the Data Protection Act.
"Let us not forget that this information would have been all a criminal would ever need to carry out identity fraud. Today's penalty reflects the seriousness of this case."
In other news, the ICO recently had to return a 250,000 fine it imposed on Scottish Border Council for carelessly disposing paper records, after the Information Rights Tribunal ruled that the amount was excessive.