Extension of GSTR-4 filing deadline: due date shifted to end of August under section 148 notification. The Government, under section 148 of the Central Goods and Services Tax Act, 2017, amends Notification No. 21/2019-Central Tax by substituting the figures, letters and words previously specifying the due date in the first proviso to the third paragraph for filing FORM GSTR-4 for the financial year 2019-2020 with a later date in August, thereby extending the statutory filing deadline set in the principal notification.