Due date extension for Form GSTR-4: filing for 2020-21 extended to 31 July 2021, effective retrospectively. Extension of the filing deadline for Form GSTR-4 for financial year 2020-21 by substituting the earlier due date with a later date; the amendment is effected by state notification and is deemed to have come into force from the original deadline, thereby altering the compliance timeline for taxpayers required to file the return.