“D. The First Proviso to Section 153C introduces a legal fiction on the basis of which the commencement date for computation of the six year or the ten year block is deemed to be the date of receipt of books of accounts by the jurisdictional AO. The identification of the starting block for the purposes of computation of the six and the ten year period is governed by the First Proviso to Section 153C, which significantly shifts the reference point spoken of in Section 153A(1), while defining the point from which the period of the “ relevant assessment year ” is to be calculated, to the date of receipt of the books of accounts, documents or assets seized by the jurisdictional AO of the non-searched person. The shift of the relevant date in the case of a non-searched person being regulated by the First Proviso of Section 153C(1) is an issue which is no longer res integra and stands authoritatively settled by virtue of the decisions of this Court in SSP Aviation and RRJ Securities as well as the decision of the Supreme Court in Jasjit Singh. The aforesaid legal position also stood reiterated by the Supreme Court in Vikram Sujitkumar Bhatia . The submission of the respondents, therefore, that the block periods would have to be reckoned with reference to the date of search can neither be countenanced nor accepted.