Please make sure that from the quarter January – March 2021 onwards, you will be assigned to QRMP scheme by the GST System. You can choose to opt out from the QRMP scheme and if so, you would need to file both Form GSTR-1 and Form GSTR-3B on Monthly frequency.
However, you may continue to remain in the QRMP scheme and file both Form GSTR-1 and Form GSTR-3B at quarterly frequency.