Capital gains computation: proviso limiting indexed cost substitution to qualifying pre-enactment transfers, with retrospective effect. Clause 20 narrows the second proviso to section 48 by limiting the substitution of the phrases 'cost of acquisition' and 'cost of any improvement' with 'indexed cost of acquisition' and 'indexed cost of any improvement' to cases where the long-term capital asset transfer occurred before 23rd day of July, 2024; the amendment is to be read as having retrospective effect from that date and does not affect the exception for non-resident transfers of specified shares or debentures.