ISA stands for Individual Savings Account.
The main difference between an ISA and any other savings account is that it offers tax-free interest payments, so you could get more for your money.
There is a limit to how much money you can put into an ISA in each tax year, which is called the ‘ISA allowance’. The ISA allowance for the 2019/20 tax year is £20,000.
You can only have one ‘active’ cash ISA every year – this means, for example, that you can’t open multiple ISAs in a single tax year, and benefit from the tax-free savings allowance in every one of these cash ISAs.
You can, however, split your allowance between several cash ISA products. So you could open two or three Nationwide cash ISAs and, as long as you don’t exceed your annual ISA allowance in the total deposits you put in across all of them, you can use them all.