SolvedCH182740 | Dishonest tax agents: file access notice: documents and information that cannot be requested: not in a person's possession or power
From HM Revenue & Customs · Compliance Handbook
We cannot require a person to produce a document unless
the document is in their possession, or
they have the power to produce it.
‘In their possession’ means that the person has physical control over the document. It does not matter who the document belongs to.
‘In their power’ means the person has the ability to get the document, or a copy of it, from whoever holds it.
This ability to get the document can be through
a legal entitlement to make the person holding the document give it to them, or
the influence that the person has on the person who owns or possesses the document.
We do not need to be able to prove that a document is in a person’s possession or power before requiring them to produce it.
However, the person will not have failed to produce the document (or a copy of it) if they can satisfactorily show
that it is not in their possession or within their power to produce, or
why they are unable to produce a document that is within their power.
The onus is on the person to produce the document.