Some common reasons switches fail are:

1. The details you provided to us do not match the details held at your old bank (e.g. you have got married and have not changed your maiden name to your married name). Please make sure your details are fully up to date at your old bank and Starling before initiating a switch. 
2. You are trying to switch a different type of account to the account you have opened at Starling (e.g. you held a sole trader account and you are now switching to a business current account). Please check the account type with your old bank and then you can request a new switch.
3. You are trying to switch a savings account - unfortunately, you cannot switch a savings account as part of the Current Account Switch Service.

Normally if a switch has been rejected you’ll be able to fix the problem and make a new switch request. Check with your old bank or Starling customer service for the details.