of clause (b) of sub-section (1) of Section 149 as they stood immediately before the commencement of the Finance Act, 2021. As per this proviso thus no notice under Section 148 would be issued for the past assessment years by resorting to the larger period of limitation prescribed in newly substituted clause (b) of Section 149(1). This would indicate that the notice that would be issued after 01.04.2021 would be in terms of the substituted Section 149(1) but without breaching the upper time limit provided in the original Section 149(1) which stood substituted. This aspect has also been highlighted in the memorandum explaining the proposed provisions in the Finance Bill. If according to the revenue for past period provisions of section 149 before amendment were applicable, this first proviso to section 149(1) was wholly unnecessary. Looked from both angles, namely, no indication of surviving the past provisions after the substitution and in fact an active indication to the contrary, inescapable conclusion that we must arrive at is that for any action of issuance of notice under Section 148 after 01.04.2021 the newly introduced provisions under the Finance Act, 2021 would apply. Mere extension of time limits for issuing notice under section 148 would not change this position that obtains in law. Under no circumstances the extended period available in clause (b) of subsection (1) of Section 149 which we may recall now stands at 10 years instead of 6 years previously available with the revenue, can be pressed in service for reopening assessments for the past period. This flows from the plain meaning of the first proviso to sub-section (1) of Section 149. In plain terms a notice which had become time barred prior to 01.04.2021 as per the then prevailing provisions, would not be revived by virtue of the application of Section 149(1)(b) effective from 01.04.2021. All the notices issued in the present cases are after 01.04.2021 and have been issued without following the procedure contained in Section 148A of the Act and are therefore invalid.