“18 Confidentiality (1) Revenue and Customs officials may not disclose information which is held by the Revenue and Customs in connection with a function of the Revenue and Customs. (4) In this section— … (c) a reference to a function of the Revenue and Customs is a reference to a function of— (i) the Commissioners, or (ii) an officer of Revenue and Customs …”
“23 Freedom of information (1) Revenue and customs information relating to a person, the disclosure of which is prohibited by section 18(1), is exempt information by virtue ofsection 44(1)(a) of the Freedom of Information Act 2000 (prohibitions on disclosure) if its disclosure— (a) would specify the identity of the person to whom the information relates, or (b) would enable the identity of such a person to be deduced. (1A) Subsections (2) and (3) of section 18 are to be disregarded in determining for the purposes of subsection (1) of this section whether the disclosure of revenue and customs information relating to a person is prohibited by subsection (1) of that section. (2) Except as specified in subsection (1), information the disclosure of which is prohibited by section 18(1) is not exempt information for the purposes ofsection 44(1)(a) of the Freedom of Information Act 2000 . (3) In subsection (1) ‘revenue and customs information relating to a person’ has the same meaning as in section 19.”
“…information about, acquired as a result of, or held in connection with the exercise of a function of the Revenue and Customs (within the meaning given by section 18(4)(c)) in respect of the person; but it does not include information about internal administrative arrangements of Her Majesty's Revenue and Customs (whether relating to Commissioners, officers or others).”