This part of the law is not yet in force so the absence of detailed guidance is perhaps excusable. However not entirely as data is now being submitted which will become accessible and we do not really know exactly on what basis it will be accessible. Other than “trust us, we’re HMRC”. I don’t, but you “may not possibly comment”.
Via the Ministry of Justice, “God”, (keywords: legitimate expectation and FOI) I had a reply, as one inevitably does, from “Satan” viz HMRC but a very significant part and level of HMRC. Most constructively about, in principle, certain sensitive aspects of this issue. I get it that HMRC cannot disseminate opinions they have not yet officially formed (even if they should have). Sometimes I feel that they are just unaware of the extent to which such views have insinuated themselves (rightly or wrongly) into the fabric of modern jurisprudence and so into the body of law with which our clients and insurers and even the judiciary expect us to be familiar. Law, and I would say quasi-law such as HMRC’s settled opinions, must be publicly available. See most recently Lord Reed REFERENCES (Bills) by the Attorney General and the Advocate General for Scotland - United Nations Convention on the Rights of the Child and European Charter of Local Self-Government (Incorporation) (Scotland)  UKSC 42 (06 October 2021) at 75-77
I hope to be able to provide some feedback to this forum. Whatever the strict legalities and nicety of good manners I may have to apply a self-denying ordinance. It is unwise to jeopardise one’s personal supply by outing one’s dealer!