Recovering my government gateway user ID
HMRC have a special section on their website for anyone who has lost or forgotten their User ID. This link will take you to the appropriate page.
You can then click on this link to go through the process to recover your User ID.
If you still have the email address you used when you first registered for your Personal Tax Account, you will be sent a code to that address. If you can’t remember the email address you used, or it is no longer in use, you will be asked which kind of Tax account you have.
Depending on which one you choose, you will then be given the appropriate helpline telephone number and a note of the line’s opening hours.
You can then choose whether you want your recovered ID number to be sent by post (which may take up to ten days to arrive) or by text message to your mobile phone.