Customers of Precise were written to after a break-in took place and physical hardware was stolen on 7 October. Around 11,000 savings customers with the lender’s sister firm Charter Savings Bank have also received letters.
Parent firm Charter Court Financial Services kept the break-in quiet while it worked with police and independent experts in investigating the crime.
Charter Court said the incident was not associated with cybercrime or hacking of computer systems, much like the hack of some 20,000 Tesco Bank accounts that was confirmed last month.
In a statement Charter Court said: “Based on our investigations, working with independent experts and the police, we believe that the personal computers were the motivation for the theft rather than any data.
“While we have no evidence to suggest any personal customer data has in fact been disclosed as a result of this incident and it is unlikely that the data will be discovered, there could be an increased risk of misuse of personal data or identity theft for these customers.
“Charter Court Financial Services takes security issues very seriously and we apologise to customers for this incident.”
Extra security measures and fraud monitoring procedures have been implemented since the incident took place, with additional steps taken to prevent such an incident happening again. The bank has also paid for Experian credit and identity monitoring services for affected customers.
Money and accounts of customers remain safe and secure, the firm said, while stolen computers were not used in or linked to core banking or mortgage systems.