“The element of guess-work and the almost unavoidable inaccuracy in a properly made best of judgment assessment, as the cases have established, do not serve to displace the validity of the assessments, which are prima facie right and remain right until the taxpayer shows that they are wrong and also shows positively what corrections should be made in order to make the assessments right or more nearly right. It is also relevant, when considering the sufficiency of evidence to displace an assessment, to remember that the facts are peculiarly within the knowledge of the taxpayer.”
“14. In my judgment, contemporaneous written documentation is of the very greatest importance in assessing credibility. Moreover, it can be significant not only where it is present and the oral evidence can then be checked against it. It can also be significant if written documentation is absent. For instance, if the judge is satisfied that certain contemporaneous documentation is likely to have existed were the oral evidence correct, and that the party adducing oral evidence is responsible for its non-production, then the documentation may be conspicuous by its absence and the judge may be able to draw inferences from its absence.”