Allowing the appeal the Court held that ,after issuing a notice under S. 148, he accepts the contention of the assessee and holds that the income which he has initially formed a reason to believe had escaped assessment, has as a matter of fact not escaped assessment, it is not open to him independently to assess some other income-If he intends to do so, a fresh notice under section 148 would be necessary. Assessing Officer has no power to reassess other income not mentioned in notice under S 148.Explanation 3 to section 147 was inserted by the Finance (No. 2) Act of 2009. The effect of the Explanation is that once an Assessing Officer has formed a reason to believe that income chargeable to tax has escaped assessment and has proceeded to issue a notice under section 148, it is open to him to assess or reassess income in respect of any other issue though the reasons for such issue had not been included in the reasons recorded under section 148(2) . However, Explanation 3 does not and cannot override the necessity of fulfilling the conditions set out in the substantive part of section 147. An Explanation to a statutory provision is intended to explain its contents and cannot be construed to override it or render the substance and core nugatory. Section 147 has this effect that the Assessing Officer has to assess or reassess the income (“such income”) which escaped assessment and which was the basis of the formation of belief and if he does so, he can also assess or reassess any other income which has escaped assessment and which comes to his notice during the course of the proceedings. However, if after issuing a notice under section 148, he accepts the contention of the assessee and holds that the income which he has initially formed a reason to believe had escaped assessment, has as a matter of fact not escaped assessment, it is not open to him independently to assess some other income. If he intends to do so, a fresh notice under section 148 would be necessary. Accordingly, if the Assessing Officer was to reopen the finding rendered in the scrutiny assessment, it would clearly amount to change of opinion, which was impermissible. The reassessment was not valid. (AY. 1997-98)