Each file is inspected to work out which return it belongs to — GSTR-1 (outward supplies), GSTR-2A (inward supplies, invoice detail), or GSTR-2B (inward supplies, ITC statement — both the invoice-detail file and the separate ITC-summary file the portal sometimes exports). Months of the same return type merge into one shared set of sheets. All the processing runs in a background thread, so even very large uploads won't freeze this page — you'll just see a status message while it works.

• GSTR-1 → Summary, B2B Invoices, B2CL, CDNR, CDNRA, CDNUR, HSN Summary, Doc Issue Summary, B2CS Summary, Nil Rated Summary.
• GSTR-2A → Summary, B2B Inward Supplies, B2B Amendments, Credit-Debit Notes, ISD Credit, TDS Credit, E-Commerce Supplies.
• GSTR-2B → Summary (with official period ITC totals), ITC Summary, B2B Invoices, B2B Amendments, CDNR, ISD Credit.
• Any other section (or a GSTR-6 file) still gets pulled out and merged with readable column names — just not the fully polished layout above yet.
• Very large uploads (hundreds of thousands of rows) can take a while to encode — that's normal; the page stays responsive throughout.