"may by notice in writing require a person (the "taxpayer") - (a) to provide information, or (b) to produce a document if the information or document is reasonably required by the officer for the purposes of checking the taxpayer's tax position."
"Information and supporting documents in relation to all UK and foreign property transactions you have been involved in ... during the last 20 years "information and supporting documentation in relation to any assets disposed of ... in the last 20 years."