Amendment to Fourth Schedule extends applicability timeframe by substituting the prior deadline and deeming substitution effective from start of year. The amendment replaces the date in the first proviso to rule 3 of Part A of the Fourth Schedule to the Income-tax Act with a later cutoff and provides that this substitution is deemed to have effect from the first day of the following year, thereby adjusting the applicability timeframe established by that proviso without altering other substantive terms.