This discussion clarifies the GSTR 3B filing deadlines for April 2020. The due date depends on your aggregate turnover from the preceding financial year. Taxpayers with turnover over £5 crore must file by 24th June 2020, those between £1.5 crore and £5 crore have until 30th June 2020, and those with turnover up to £1.5 crore can file by 6th July 2020.