Do I need to switch to Zopa to earn cashback?

No. You don’t need to switch your existing bank account to open a Biscuit current account or start earning cashback. You can use Biscuit alongside another current account if that works better for you. 

If you choose cashback on bills, you’ll need to pay eligible Direct Debits from your Biscuit current account to earn cashback on them. You can move those Direct Debits without moving all your banking to Zopa.