This was compared to just 11,295 bank account customers who left Nationwide in that period. The switching rush in recent years has been driven by the building society's generous cash bribes. Around 1million bank account switches took place in total in the past 12 months, figures from the Cass show. October was the busiest month tor bank switches with 128,199, followed by November with 124,650, and December 97,265. NatWest saw 8,731 net switchers and TSB gained 4,690 more customers than it lost, while HSBC, RBS, Danske and Triodos gained 6,357 net switching customers between them.