Cash ISA savers can get up to £500 cashback as part of a new switching incentive from Barclays, but there is a catch. You could get up to £500 cashback by transferring your cash ISA to Barclays. Here is how Barclays’ ISA transfer cashback offer works. What is Barclays ISA transfer cashback offer? The transfer can be made into a new or existing Barclays cash ISA either through the ISA transfer service in the Barclays app or via online banking.