GSTR-1 for October 2026 by 11 November: a Table 12 HSN (B2B and B2C) and Table 13 documents sheet for CA firms

Updated 26 Oct 2026 · Disclosure: the white-label calendar linked below is an Unadhi product (₹999/year). This guide is for information only, not professional advice.

What you get: a ready-to-copy Google Sheet layout that gets every client's October 2026 GSTR-1 past the Table 12 and Table 13 checks before 11 November. Tab 1 holds HSN rows split into B2B and B2C, with a formula that flags codes shorter than the client must report (4 or 6 digits, from FY 2025-26 turnover). Tab 2 ties the Table 12 totals back to the B2B and B2C values in the other GSTR-1 tables, one row per client. Tab 3 is a Table 13 document log (series, from, to, cancelled, net issued). Tab 4 filters the clients still open. You also get a made-up example, a plan for 2 to 11 November and a WhatsApp message for clients.

Short answer (checked 26 Oct 2026): monthly GSTR-1 for October 2026 is due by Wednesday 11 November 2026. Since the May 2025 return period (GSTN Phase 3), HSN codes in Table 12 can only be picked from a dropdown, Table 12 has separate B2B and B2C tabs, and the B2B tab cannot be empty when B2B supplies appear elsewhere in the return. Clients with aggregate turnover up to ₹5 crore in the previous year report at least 4 digits; above ₹5 crore, 6 digits. Table 13 (documents issued) is mandatory: the portal stops you at summary stage if it is blank. The value checks between Table 12 and the other tables were announced in warning mode; GSTN said Phase 4 would be "communicated in due course", and we found no Phase 4 advisory, so check the portal before you rely on that.

What the portal checks

• Digits: 4 or 6, decided by aggregate annual turnover of the preceding financial year (Notification 78/2020-Central Tax). For returns in FY 2026-27, use FY 2025-26 turnover. A client that crossed ₹5 crore last year needs 6-digit codes from April 2026.
• B2B tab: compared with the B2B values in Tables 4A, 4B, 6B, 6C, 8 (registered), 9A, 9B (registered), 9C (registered), 15 and 15A (registered recipient).
• B2C tab: compared with Tables 5A, 6A, 7A, 7B, 8 (unregistered), 9A (export and B2CL), 9B and 9C (unregistered), 10, 15 and 15A (unregistered recipient).
• Amendments: only the difference is taken for the check.
• Table 13: an error appears if B2B or B2C supplies are reported and Table 13 is blank.
• Help on the portal: a "Download HSN Codes List" button in Table 12 gives the current HSN and SAC list as Excel, and "Product Name as in My Master" fills HSN, description, UQC and quantity from your saved master.

Tab "HSN rows": one row per client, per HSN, per B2B or B2C

Tab "Clients": column A client, column B FY 2025-26 aggregate turnover (₹), column C =IF(B2>50000000,6,4). Fill column B once a year from last year's returns.

Tab "Tie-out": one row per client

"9 Nov" in the status is our working rule (two days before the due date), not a legal date. A small rounding difference can be fine; a large one usually means an invoice went into the wrong tab or a credit note was left out.

Tab "Docs": Table 13, one row per document series

Keep one row per series. A client with a separate series for each branch or for e-commerce sales needs one row for each, because serials must run in order within a series (rule 46 asks for a consecutive serial number of up to 16 characters).

Tab "Open": who is not ready

Use =FILTER('Tie-out'!A2:K,'Tie-out'!K2:K<>"FILED",'Tie-out'!K2:K<>"READY"), then sort so "STOP" rows come first. Add columns for who chases the client and the date they promised the sales register.

Made-up example (not a real client)

Client "Sample Hardware" had FY 2025-26 turnover of ₹6.2 crore, so Clients!C shows 6. Its October sales register has 3 HSN codes. One row was entered as 7318 (4 digits): column E shows "SHORT: need 6 digits", so you change it to the 6-digit code from the register. B2B taxable value in Table 4A is ₹18,40,000 and the B2B rows in Table 12 add up to ₹18,10,000: a ₹30,000 difference, traced to one credit note left out of the HSN rows. B2C value ₹2,60,000 matches. Table 13 has two rows (invoices 0412 to 0517 with 2 cancelled, so 104 net; credit notes 0031 to 0033). After the fix the status reads READY and the return is filed on 10 November.

Plan for 2 to 11 November

• Mon 2 Nov: ask every client for the October sales register with HSN, UQC and quantity, plus the list of cancelled invoices and credit notes.
• Thu 5 Nov: fill the HSN rows and Docs tabs; fix every SHORT code using the portal's "Download HSN Codes List".
• Mon 9 Nov: our working target. Every client READY on the Tie-out tab, draft GSTR-1 saved on the portal.
• Wed 11 Nov: legal last day for monthly GSTR-1. File, record the ARN date in column J.
• 11 to 20 Nov: if something was wrong after filing, see our GSTR-1A guide below; GSTR-3B for October is due 20 November.

WhatsApp message to a client

"Hello, GSTR-1 for October is due on Wednesday 11 November. The GST portal now needs every HSN code picked from its list, split into B2B and B2C sales, and a list of invoice numbers used and cancelled. Please send your October sales register with HSN, unit and quantity, and the numbers of any cancelled invoices or credit notes, by Monday 2 November so we can file by the 9th."

Related guides

• GSTR-1 chase list before the 11th
• GSTR-1A for October 2026: fix GSTR-1 before GSTR-3B
• Rule 46 tax invoice fields and the 16-character serial
• Quarterly GSTR-1 and IFF due dates for QRMP filers
• November 2026 due-date chase list for CA firms

Partner programme opening soon

Partner programme opening soon: join the free waitlist. Planned terms are 50% of each referred sale (75% once you have 5+ paying customers), single level, paid through Gumroad only from revenue received.

Sources

• GSTN advisory: Reporting of HSN codes in Table 12 of GSTR-1/1A (Phase 3 from May 2025 return period; B2B/B2C tabs; dropdown only; value checks in warning mode; Phase 4 to be communicated)
• GST Council newsletter, May 2025 (portal update of 1 May 2025: Table 12 Phase 3 and Table 13 mandatory)
• Text of the GSTN advisory of 1 May 2025 on Table 12 and Table 13 (third-party copy)

← All guides

Unadhi Guides are free, independent explainers. We correct errors as soon as we find them: write to mininglife7@gmail.com.