Extension of GSTR-3B filing deadline granted by substituting the notified date under section 168 and rule 61(5). Extension of the filing deadline for FORM GSTR-3B for December 2017 is effected by notification 1-A/2018 which, exercising statutory powers, substitutes the previously notified date in the Table of the earlier CCT notification (1-K/2017) at serial number 5, column (3) with a later date, thereby amending the compliance timeline for that entry.