Barclays confirmed that, during that incident, more than half of attempts to make an online payment failed. "We acknowledge that through no fault of their own, some of our customers and clients may have suffered loss or distress and inconvenience," UK chief executive Vim Maru wrote in the letter published by the Treasury Committee. The outage occurred because of a software problem in a part of its UK mainframe operating system, and was not triggered by a cyber attack, Barclays told the committee. Across the nine banks and building societies, there have been at least 158 IT failure incidents between January 2023 and February 2025, according to estimates they provided. That figure does not include Barclays' recent outage, nor disruption to other banks' online services in more recent weeks. Common reasons given for the incidents include problems with third-party suppliers, disruption caused when systems were changed, and internal software malfunctions.