Revolut, Barclays and Monzo top fraud complaints rankingRevolut topped the FOS complaints rankings. Challenger banks Revolut and Monzo have topped the rankings for fraud and scam complaints filed to the Financial Ombudsman Service (FOS) as Brits flock towards digital offerings. Fintech juggernaut Revolut received the most amount of APP fraud complaints referred to the FOS at 1,875. This towered above Barclays’ 31 per cent and beat peer Revolut, which had 30 per cent upheld. Revolut leaning into AI to fight fraudThe APP figures, revealed by Which?, are almost mirrored across other fraud and scam complaints.