Extension of filing period under state GST notifications by substituting the proviso's date range and deadline. The Commissioner, under section 168 read with sub rule (5) of rule 61, amends notification No. 9/2017 State Tax and No. 1/2018 State Tax by substituting the proviso's previously stated month range and terminal date with a later month range and a later terminal date, thereby extending the temporal application of those notifications without altering other substantive provisions.