Millions of NatWest and RBS customers left high and dry This is a technical problem affecting a large number of NatWest and Ulster Bank customers, and a small number of RBS customers, including some of our business customers. The main problem customers are having is that where people have had money go into their accounts overnight, there may be a delay in it showing up on their balance," the spokesman said. Up to eight million personal and business customers may have been affected. Consumer groups called for customers to be compensated. Sarah Brooks, director of financial services at Consumer Focus said: "This will have been a frustrating time for all customers affected, given how reliant a lot of us are on our bank accounts for day to day living. We hope that the problem will be resolved quickly and doesn't happen again. The problem also affected over 100,000 Ulster Bank customers in Northern Ireland. The bank is owned by RBS Group.