How to read it
"Complaints per 1,000 accounts" is the FCA's provision measure: complaints opened in the period divided by accounts in force. A bank with 30 million accounts and 90,000 complaints scores 3.0; a bank with 3 million and 9,000 scores the same. A low score with a high upheld rate means few complaints but the bank agreed with most of them; a high score with a low upheld rate means many complaints that the bank mostly rejected. Neither is a measure of financial safety, which the FSCS covers regardless.
Firms report on their own half-year cycles, so the windows differ: most big banks report calendar halves, while Monzo, Starling and Nationwide report April to September. Firms with fewer than 500 complaints in a half year do not appear. Revolut does not appear in the FCA's file at all. Some firms report jointly for a group; those rows cover more than one brand.
Source: FCA, firm-level complaints data, published twice a year and revised in place. Reused under the Open Government Licence v3.0. Figures are the FCA's; percentages are of complaints closed in the period.