Judgment :- R. JAYASIMHA BABU, J. The Tribunal has held that the assessee had disclosed all primary and material facts to the WTO and that the reopening of the assessment under s. 17(1)(a) of the WT Act was not warranted. The asset in question is the building in which the assessee had a share. The construction of the building was completed and the same was occupied in October, 1968. The valuation of building was required to be made as on 31st December, 1970. The assessee valued the land and the building separately and for the building he adopted the cost of construction. The valuation so made had been accepted by the WTO. In the return filed by the assessee, he had valued the building at Rs. 22, 93, 650. The WTO completed the original assessment on 19th February, 1972. The same was reopened and fresh assessment order was made on 28th July, 1977 wherein the value of the building was determined as Rs. 52, 61, 500. On appeal to the CWT(A), he fixed the value at Rs. 50, 00, 000. On further appeal to the Tribunal, the Tribunal held that the reopening itself was not warranted. The Tribunal has noticed the fact that as on the date of valuation, the assessee was not in possession of any material which showed the value different from the one declared by it. The WTO and the CWT(A) referred to the valuation report which had been submitted by a private valuer to the assessee in August, 1971 valuing the building Rs. 35, 70, 814. That report, however, was not a report which the assessee was required to submit at the time of the assessment. That report was not regarding the value as on the valuation date which was relevant for the purpose of assessment for 1971-72. The WTO was of the view that the value furnished in the return filed by the assessee was not the correct value and it was open to him to adopt different value. He, however, did not do so. His omission to adopt a different value cannot now be regarded as a failure on the part of the assessee to disclose the material facts fully and truly. Even in the reassessment, the value adopted is not the valuation given by the valuer in August, 1971, but much higher than that figure. He, however, did not do so. His omission to adopt a different value cannot now be regarded as a failure on the part of the assessee to disclose the material facts fully and truly. Even in the reassessment, the value adopted is not the valuation given by the valuer in August, 1971, but much higher than that figure. The assessee cannot be held responsible for not valuing the building at the figure at which the WTO and the CWT(A) now wish to value of the buildingThe Tribunal has rightly stated that the assessee had disclosed all the primary and material facts. Any omission thereafter in correctly valuing the building was omission of the WTO and is not to be attributed to any failure on the part of the assessee to fully and truly disclose the relevant facts. Even after the completion of the assessment, the WTO had the opportunity to reopen the assessment provided it was done within the time limit, under s. 17(1)(b) of the Act. That also he failed to do. His initiation of the proceedings, thereafter by relying on s. 17(1)(a) of the Act cannot be upheld as there had been no failure on the part of the assessee to disclose the relevant material fact fully and truly. The very fact that the statute makes a distinction between cases were the underassessment is due to the assessee's failure to fully and truly disclose the material facts and the other cases would show that every case of underassessment cannot be attributed to assessee's failure to disclose the facts fully and truly. Underassessment by itself cannot, be justification to resort to s. 17(1)(a) of the Act. It is expected of all the AOs that they should be vigilant not only at the time of assessment, but also within the period prescribed for reopening of assessments, even where there has been no failure on the part of the assessee to truly and fully disclose the material facts. If the AOs are not alert and allow the time to elapse and they cannot, therefore, as a matter of course, seek to justify the reopening by casting the blame on the assessee. Assessees are expected to place before the AOs all the primary facts and not suppress anything that is material. If the AOs are not alert and allow the time to elapse and they cannot, therefore, as a matter of course, seek to justify the reopening by casting the blame on the assessee. Assessees are expected to place before the AOs all the primary facts and not suppress anything that is material. Once that is done it is for the AO to accept it or make his own estimate of the amounts required to be considered for the purpose of assessmentWe do not find any error in the order of the Tribunal. The question referred to us, namely, "Whether, on the facts and in the circumstances of the case the Tribunal is justified in law in holding that the provisions of s. 17(1)(a) of the WT Act are not attracted in this case and accordingly in cancelling the reassessment made for the year 1971-72." is answered in favour of the assessee and against the Revenue.