Evidence of fact: meaning of comes to their knowledge
Only the assessing officer can say when the necessary evidence of facts was obtained, that is, when the facts relied upon for the assessment that was made became known.
Knowledge in this context refers to actual knowledge, not what has been referred to as constructive knowledge. It is the actual facts known to HMRC that are pertinent, not what they could have, or ought to have found out.
The fact that the information was available during an assurance visit, but the officer failed to recognise the significance of the information, does not fulfil the requirements of the law.
We are protected in this viewpoint by the High Court decision in the appeal case Van Boeckel, QB Dec 1980  STC 290 and The Post Office, QB, May 1995  STC 749. This was a VAT case but applies equally to excise.
Significance of “the” assessment
Note: Section 12(4)(b) and 12A(4)(b) both refers to the making of the assessment, not an assessment. Therefore the clock starts ticking under the one year rule when the last piece of material evidence comes to the attention of HMRC which justifies the raising of the assessment in question.
A taxpayer may argue that an assessment is out of time under the one year rule because evidence to justify the making of an assessment was available to or held by HMRC more than one year earlier.
However, the pertinent question is - ‘When was the piece of information received by HMRC that was necessary in the opinion of the assessing officer to make the assessment that was made’, not one that could have been made. Therefore for practical purposes ‘evidence of facts’ should be construed as evidence of facts giving rise to a particular assessment.