SolvedCH177170 | Sanctionable conduct by tax advisers: file access notice: documents and information that cannot be requested: appeal material
From HM Revenue & Customs · Compliance Handbook
We cannot require a person to provide information or produce a document that relates to the conduct of a pending tax appeal.
A document that ‘relates to the conduct of a pending appeal’ is a document that has been brought into existence as part of the preparation for the presentation of a tax appeal.
The exclusion does not cover, and therefore we can request, information or documents that may be used in presenting the appeal, for example as evidence, but which existed before the appeal process began.