'8....... In such a situation, it was not possible for the Sales Tax Officer to find out precisely the turnover suppressed. He could only make an estimate of the suppressed turnover on the basis of the material before him. So long as the estimate made by him is not arbitrary and has nexus with facts discovered, the same cannot be questioned. In the very nature of things the estimate made may be an over-estimate or an underestimate. But that is no ground for interfering with his 'bestjudgment'. It is true that the basis adopted by the officer should be relevant to the estimate made. The High Court was wrong in assuming that the assessing authority must have material before it to prove the exact turnover suppressed. If that is true, there is no question of 'best-judgment' assessment. The assessee cannot be permitted to take advantage of his own illegal acts. It was his duty to place all facts truthfully before the assessing authority. If he fails to do his duty, he cannot be allowed to call upon the assessing authority to prove conclusively what turnover, he had suppressed. That fact must be within his personal knowledge. Hence the burden of proving that fact is on him. No circumstance has been placed before the assessing authority to show that the assessee's dealings during September 1, 1950 to September 19, 1960, outside his accounts were due to some exceptional circumstance or that they were proportionately more than his dealings outside his accounts, during the remaining periods. The assessing authority could not have been in possession of any correct measure to find out the escaped turnover during the periods November 1, 1959 to August 31, 1960
