Every registered person files a statement of outward supplies (GSTR-1 or IFF) and a summary return with tax payment (GSTR-3B) on the cycle that applies to them — monthly, or quarterly under the QRMP scheme. The two returns have to tell the same story as the books.
We pull invoices from the accounting system, match input credit with GSTR-2B, compute RCM and interest where due, file the returns, and keep a month-wise working paper. The aim is a clean 2B match and no late fee that could have been avoided by filing on the due date.