639. Powers to obtain information and documents.

An officer of Revenue and Customs1 may by notice in writing (a 'taxpayer notice') require a person ('the taxpayer') to provide information or to produce a document2, if the information in the document is reasonably required by the officer for the purposes of checking3 the taxpayer's tax position, or the tax position of another person whose identity is known to the officer4. 'Tax position', in relation to a person, means the person's position as regards any tax5, including the person's position as regards: (1) past, present and future liability to pay any tax; (2) penalties and other amounts that