The process of a Bed and ISA involves selling your investments in a GIA and then reinvesting the proceeds in an ISA. This means you're moving your money from a taxed account to a tax-efficient account. By reinvesting the proceeds in an ISA you protect your future gains from tax. However, selling your investments in your GIA could lead to a capital gain or loss which means you may have tax to pay on these investments. You can read more about capital gains tax allowance here.