To prepare your bills for GSTR-1, make sure every sales invoice has a unique sequential number, the correct GSTIN and HSN code, and is sorted into B2B (registered buyers) vs B2C (consumers). Reconcile your invoice register against your books before you upload, so totals, tax splits, and the HSN summary all tie out. This checklist walks through each step.
Quick answer: your pre-GSTR-1 checklist
- All invoices are numbered sequentially with no gaps or duplicates
- Each invoice shows a valid 15-digit GSTIN (yours, plus the buyer's for B2B)
- Sales are split into B2B, B2C-large (>₹1 lakh inter-state), and B2C-small
- Correct HSN/SAC code on every line (4-digit if turnover ≤ ₹5 cr, 6-digit if above) — the full set is in our GST bill mandatory-fields checklist
- CGST + SGST (intra-state) or IGST (inter-state) applied correctly
- Credit/debit notes for the period are recorded
- Invoice register totals match your books before upload
Why bill data matters for GSTR-1 (and why it matters)
| Bill element | What to check | Why it matters |
|---|---|---|
| Invoice number | Unique, consecutive, ≤ 16 characters, no mid-year restart | Rule 46 requirement; gaps or duplicates break the audit trail and trigger notices |
| Invoice date | Falls inside the return period | Decides which month/quarter the supply is reported in |
| Your GSTIN | Valid 15-digit number on every tax invoice | Identifies you as the supplier; invalid GSTIN invalidates the invoice |
| Buyer GSTIN (B2B) | Correct and active | Mismatched GSTIN means your buyer can't claim input tax credit from GSTR-2B |
| Place of supply | State of the buyer | Decides CGST+SGST vs IGST; wrong choice causes tax-head errors |
| HSN/SAC code | 4 or 6 digit per your turnover slab | Mandatory in Table 12 HSN summary; wrong codes cause mismatch flags |
| Taxable value & rate | Matches the line items | Feeds rate-wise totals; errors cascade into your tax liability |
| Tax amount (CGST/SGST/IGST) | Computed on taxable value | Must reconcile with your books and GSTR-3B |
Sample invoice register (ready for GSTR-1)
This is how a clean outward-supplies register looks before upload — the exact data you transcribe into the GSTR-1 tables.
Mathew Industrial Supplies Pvt Ltd (Prop. Thomas Mathew) 22 Banerji Road, Kochi, Kerala 682018 · GSTIN: 32AALCK7890X1Z3 Outward supplies register · Period: May 2026
| Invoice No. | Date | Buyer | Buyer GSTIN | Type | Taxable (₹) | CGST (₹) | SGST (₹) | IGST (₹) | HSN |
|---|---|---|---|---|---|---|---|---|---|
| INV-2026-0101 | 03 May 2026 | Patel Hardware | 24AAACP2233K1Z5 | B2B (inter-state) | 50,000 | — | — | 9,000 | 7308 |
| INV-2026-0102 | 09 May 2026 | Nair Traders | 32AABFN5566L1ZP | B2B (intra-state) | 40,000 | 3,600 | 3,600 | — | 7308 |
| INV-2026-0103 | 15 May 2026 | Walk-in customer | — | B2C | 8,500 | 765 | 765 | — | 7308 |
| INV-2026-0104 | 22 May 2026 | Rao Constructions | 36AADCR7788M1Z2 | B2C-large (inter-state >₹1L) | 1,40,000 | — | — | 25,200 | 7308 |
| Total | 2,38,500 | 4,365 | 4,365 | 34,200 |
Invoice INV-2026-0104 exceeds ₹1 lakh and is inter-state to an unregistered buyer, so it is reported invoice-wise in Table 5 (B2C-large), not in the consolidated B2C summary.
Sorting your bills the way GSTR-1 expects
GSTR-1 does not want one flat list — it wants your invoices bucketed. Get the buckets right and data entry is mechanical:
- B2B (Table 4): every sale to a registered buyer, reported invoice-by-invoice with their GSTIN. If you issue invoices as a freelancer or to corporate clients, most of these land here.
- B2C-large (Table 5): inter-state sales to unregistered buyers where the invoice value exceeds ₹1 lakh — reported invoice-wise.
- B2C-small (Table 7): all other consumer sales, reported as a consolidated, rate-wise summary per state. Retail counter sales typically sit here.
- Credit/debit notes (Table 9): any credit notes or adjustments issued during the period.
- HSN summary (Table 12): rate-wise, HSN-wise totals of everything you sold.
Legal & compliance specifics (FY 2025–26)
These are the rules competitors gloss over. Getting them right is what keeps your filing clean:
- Sequential numbering — Rule 46, CGST Rules: a tax invoice must carry a consecutive serial number, unique for the financial year, not exceeding 16 characters. You may use one or more series, but each must be continuous. Confirm the rule text at cbic-gst.gov.in(opens in new tab).
- HSN reporting thresholds: for FY 2025–26, taxpayers with aggregate turnover up to ₹5 crore report a 4-digit HSN; those above ₹5 crore report a 6-digit HSN in Table 12. Reporting is now largely picked from a drop-down, so codes must be valid.
- B2C-large threshold: inter-state B2C invoices above ₹1 lakh are reported individually; this threshold has been revised over time, so verify the current value on the GST portal(opens in new tab).
- QRMP scheme: businesses with turnover up to ₹5 crore can file GSTR-1 quarterly and use the Invoice Furnishing Facility (IFF) to push B2B invoices monthly. See gstcouncil.gov.in(opens in new tab) for scheme details.
- GSTR-1 ↔ GSTR-3B ↔ GSTR-2B linkage: your GSTR-1 outward data auto-populates your buyers' GSTR-2B. Mismatches block their input tax credit — a frequent cause of disputes. The tax-rate rules behind your invoices follow the same logic explained in our GST calculation guide.
Petrol and diesel are outside GST. If you sell fuel, those supplies are not reported in GSTR-1 the way GST goods are — they fall under VAT/state levies. Keep them in a separate ledger so they don't contaminate your GST totals.
Honesty note: GSTR-1 is a record of invoices you actually issued. Back-dating invoices, inflating B2B sales to a friendly GSTIN, or under-reporting B2C cash sales are not "adjustments" — they are tax evasion. Clean record-keeping protects you; fabrication invites penalties and interest.
Prepare a compliant invoice in 2 minutes
The cleanest way to keep a GSTR-1-ready trail is to issue every bill from one place so numbering and tax splits stay consistent. Using the bill & invoice generator:
- Enter your business details — name, address, and GSTIN (saved for reuse).
- Let the tool number invoices sequentially so you never get a gap or duplicate.
- Add the buyer's GSTIN for B2B sales; leave it blank for B2C — this is your sort key later.
- Pick the HSN/SAC and rate per line; CGST+SGST or IGST is computed automatically.
- Download a clean PDF and keep the running register that maps straight onto the GSTR-1 tables.
Generator vs Word vs Excel for GSTR-1 prep
| GSTR-1 prep capability | Online generator | MS Word | Excel / manual |
|---|---|---|---|
| Gap-free serial numbering across the year | Yes Auto-increments | No You type each one | Partial Only if a formula holds |
| Picks CGST+SGST or IGST from place of supply | Yes Decided for you | No Hand-keyed | Partial Depends on your cell logic |
| Tags each sale B2B / B2C-large / B2C-small | Yes Built-in sort key | No No concept of it | Partial Extra column to maintain |
| Validates the 15-digit buyer GSTIN | Yes Format-checked | No Typos slip through | Partial Manual eyeballing |
| HSN/SAC captured on every line for Table 12 | Yes Prompted per item | No Easily forgotten | Partial Easy to leave blank |
| Exports a register that maps onto GSTR-1 tables | Yes Ready to transcribe | No Rebuild by hand | Partial If you designed it that way |
| Chance of a mismatch notice at filing | Low | High | Medium |
Common mistakes to avoid
- Skipped or duplicate invoice numbers — the single most common cause of GSTR-1 notices; one missing number breaks the whole series.
- Wrong buyer GSTIN — a single transposed digit moves a B2B sale out of your buyer's GSTR-2B and blocks their ITC.
- CGST+SGST where IGST applies (or vice-versa) — caused by the wrong place of supply; the totals tie out but the tax heads are wrong.
- Missing or incorrect HSN codes — Table 12 won't reconcile, and the portal now validates codes against a master list.
- Forgetting credit/debit notes — un-reported notes inflate your taxable turnover versus your books.
- Filing before reconciling — once GSTR-1 is filed you can only amend in the next period; check register-vs-books totals first.
Sources & references
- CBIC GST Portal(opens in new tab) — CGST Rules (Rule 46), GSTR-1 format, HSN and B2C thresholds
- GST Council(opens in new tab) — QRMP scheme and return-filing notifications
- Income Tax Department(opens in new tab) — PAN/turnover linkage for reporting thresholds
- India Code(opens in new tab) — CGST Act, 2017 (statutory text)
Want a GSTR-1-ready invoice trail without spreadsheets? Create a compliant bill free → — sequential numbering, auto GST split, instant PDF.