I've forgotten what email address I registered to log in to My Account with

The next time you go to log in, click on ‘Forgotten which email address you registered with?’, under the box where you enter your email address. You’ll be taken to a page where you can enter your United Utilities account number OR your supply address. We’ll then ask you for the answer to your security question and, once you have successfully answered the question, your email address will be displayed.