GSTR-3B is a monthly self-declaration to be filed by a registered GST dealer along with GSTR 1 return forms. It is a simple return to declare summary GST liabilities for a tax period. IMPORTANT: You have to file GSTR-3B even when there has been no business activity (nil return). You cannot revise/amend GSTR3B.
You have to file a separate GSTR 3B for every GSTIN you have. Late fees for filing GSTR-3B after the due date are:
Rs. 50 per day of delay
Rs. 20 per day of delay
For taxpayers having nil tax liability for the month If the GST amount is not paid until after the due date, taxpayers are responsible for paying interest of 18 percent per annum. Interest will be calculated from the day following the due date, to the date of actual payment.