Key points
- Close the month first: all bills, notes and purchases entered.
- Run checks for missing GSTINs, HSN codes and gaps.
- Export and file GSTR-1 by the 11th.
- Reconcile purchases with GSTR-2B after the 14th.
- Prepare, pay and file GSTR-3B by the 20th.
The workflow
- Day 1–2: close the month Make sure all sales bills, credit notes and purchase bills for the month are entered. Lock the month in your ERP if possible, so nothing changes afterwards.
- Day 2–3: run checks List bills with missing or invalid customer GSTINs, missing HSN codes, zero tax or gaps in the bill series. Fix them.
- Day 3–10: GSTR-1 Export the GSTR-1 JSON and an Excel summary. Your CA reviews the Excel, uploads the JSON and files by the 11th.
- Day 14–18: GSTR-2B Download GSTR-2B, bring it into your ERP and match purchases. Accept, reject or keep pending invoices in IMS.
- Day 18: GSTR-3B summary Review output tax, eligible credit, reversals and cash payable.
- Day 19–20: pay and file Pay the cash balance and file GSTR-3B.
What to check before GSTR-1
| Check | Why |
|---|
| B2B bills have valid GSTINs | So customers get credit |
| Inter-state B2C bills above ₹1 lakh | Reported individually |
| Credit notes linked to bills | Required in the return |
| HSN summary matches sales | Table 12 must agree with the rest |
| Bill series complete | Document summary in Table 13 |
What to check before GSTR-3B
- Output tax matches the GSTR-1 you filed (correct differences through GSTR-1A).
- Credit is taken only on bills in GSTR-2B.
- Blocked credits and 180-day reversals are accounted for.
- Cash is ready for the payable amount.
How long each step should take
| Step | Manual | With clean ERP data |
|---|
| Collect and total bills | 1–2 days | Already done |
| Prepare GSTR-1 | Half a day+ | Minutes to export |
| Reconcile purchases | Often skipped | 30–60 minutes |
| Prepare GSTR-3B | Hours | Minutes to review |
Tips
- Don’t wait for month end to enter purchases.
- Fix GSTIN problems when you make the bill, not at month end.
- Share data with your CA early in the month.
- Use reminders so the dates never surprise you.
This post explains GST rules in simple words as we understand them on 28 Oct 2026. Rules and rates change, so please confirm with your CA or the official notifications before acting on it.
