GST returns — GSTR-1 and GSTR-3B from the books, frozen when prepared, amended by the difference
Prepare GSTR-1 (the portal's JSON) and GSTR-3B (the tables) for a registration and a month from the documents, the bills and the channels' TCS; download; mark filed with the ARN; read what changed since as next month's amendments; check that the ledger's output tax agrees.
Menu → Tax → GST returns. Pick the registration and the month. Prepare GSTR-1 builds the return from every invoice, restaurant bill and note the registration issued — B2B by GSTIN, B2C small by place of supply and rate, notes, advances (11A / 11B), the HSN summary, the documents issued — in the JSON the GST offline tool imports. Prepare GSTR-3B builds the tables: 3.1 outward (and inward reverse charge from the bills), 3.2 inter-state to the unregistered, 4 input credit from the approved bills (eligible and 17(5) ineligible), 6.1 payable less credit less the TCS the channels collected. Preparing freezes what the books said. Mark filed with the date and the ARN once the CA has filed on the portal; a filed period is not prepared again. Changes since filing lists every document the books now read differently — added, removed, changed — with the amendment table it belongs to (B2BA, B2CSA, CDNRA); that list is next month's amendment. Control: the output tax the ledger carries by slab for the month (the night audit's postings) against the documents' tax. They agree, or the difference is a charge posted on a folio closed in another month — the night audit taxes when charged, the return when invoiced. Nothing here files: the portal, or the CA, does that.