“The contention on behalf of the taxpayer in this case can be summarised by saying that on the facts before the tribunal it is clear, so it is contended, that the assessment in question was not valid because the commissioners had taken insufficient steps to ascertain the amount of tax due before making the assessment. Therefore it is important to come to a conclusion as to what are the obligations placed on the commissioners in order properly to come to a view as to the amount of tax due, to the best of their judgment. The very use of the word 'judgment' makes it clear that the commissioners are required to exercise their powers in such a way that they make a value judgment on the material which is before them. Clearly they must perform that function honestly and bona fide. It would be a misuse of that power if the commissioners were to decide on a figure that they knew was, or thought was, in excess of the amount which could possibly be payable, and then leave it to the taxpayer to seek, on appeal, to reduce that assessment. Secondly there must be some material before the commissioners on which they can base their judgment. If there is no material at all it would be impossible to form a judgment as to what tax is due. Thirdly it should be recognised, particularly bearing in mind the primary obligation, of the taxpayer to make the return himself, that the commissioners should not be required to do the work of the taxpayer in order to form a conclusion as to the amount of tax which, to the best of their judgment, is due. In the very nature of things frequently the relevant information will be readily available to the taxpayer, but it will be very difficult for the commissioners to obtain that information without carrying out exhaustive investigations. In my view, the use of the words ‘best of their judgment’ does not envisage the burden being placed upon the commissioners of carrying out exhaustive investigations. What the words ‘best of their judgment’ envisage, in my view, is that the commissioners will fairly consider all material before them and, on that material, come to a decision which is one which is reasonable and not arbitrary as to the amount of tax which is due. As long as there is some material on which the commissioners can reasonably act, then they are not required to carry out investigations which may or may not result in further material being placed before them.”
“The element of guess-work and the almost inevitable 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.”
“the words ‘to the best of their judgment’ permit the commissioners a margin of discretion in making an assessment; a taxpayer may only challenge the assessment if he can show that the commissioners acted outside the margin of their discretion, by acting in a way that no reasonable body of commissioners could do. In order to succeed, the taxpayer must show that the assessment was wrong in a material respect, and that if so, the mistake is such that the only fair inference is that the commissioners did not apply best judgment, as explained in Woolf J in Van Boeckel v Customs & Excise Comrs(1981) STC 290 .”
“It is between, on the one hand, an estimate of guess honestly made on such materials as are available to the commissioners, and on the other hand, some spurious estimate or guess in which all elements of judgment are missing.”
“I have referred to the judgment in some detail, because there are dangers in taking Woolf J’s analysis of the concept of ‘best judgment’ out of context. The Tribunal should not treat an assessment as invalid merely because it disagrees as to how the judgment should have been exercised. A much stronger finding is required; for example, that the assessment has been reached ‘dishonestly or vindictively or capriciously’; or is a ‘spurious estimate or guess in which all elements of judgment are missing’; or is ‘wholly unreasonable’. In substance those tests are indistinguishable from the familiar Wednesbury principles (See Associated Provincial Picture Houses Ltd v Wednesbury Corp [1948 1 KB 223 ). Short of such a finding, there is no justification for setting aside the assessment.”
“The Tribunal should remember that its primary task is to find the correct amount of tax as far as possible, on the material properly available to it, the burden resting on the taxpayer…”