CH881650 | Agent operational guidance: dishonest tax agents: establishing dishonest conduct: issuing the conduct notice
From HM Revenue & Customs · Compliance Handbook
The conduct notice must be given to the individual by hand, or posted to their last known private address.
If you have not already issued the Tax agents: Dishonest conduct factsheet (HMRC Website) enclose it with the conduct notice and see CH881300 about giving the human rights message.