HMRC have updated their guidance by removing the link to form FB12 “because you can now use form 64-8 to authorise an agent”. https://www.gov.uk/government/collections/tax-agents-and-advisors-authorisation-forms?utm_medium=email&utm_campaign=govuk-notifications-topic&utm_source=da0b7397-a8f4-472e-b9a8-4d4bdf3a0773&utm_content=daily
