What happens if I go over the annual ISA allowance?

If you’ve paid too much into your Cash ISA, we’ll reject the payment and return your money to the linked bank account it came from.

This tax year I've added more than £20,000 across both the ISA I'm transferring in and my Zopa Cash ISA, what does this mean?

The ISA transfer will fail if it's going to take you over the government's annual allowance of £20,000.

Can I transfer in an ISA balance that'll take me over the maximum balance?

You can save up to a maximum of £250,000 across your savings and Cash ISA. So you won't be able to transfer in your ISA balance if it'll take you above this limit.