GSTR-1 for August 2025 is due on September 11 — nine days from today. We just finished the August batch for 14 SMB clients (₹40 lakh to ₹38 crore turnover band, all on Tally Prime 5.x or Zoho Books). The same four reconciliation mistakes that triggered notices on the July cycle showed up again in the first six August files. This post is the exact 60-minute Tally-to-portal sprint we run, plus the four mistakes that get the GSTN portal yellow-flag treatment within a week of filing.
## The answer in 60 words
Export GSTR-1 JSON from Tally Prime via Display More Reports > Statutory Reports > GST > GSTR-1. Reconcile B2B invoice values against your e-invoice IRN log first — not against the books. Validate Table 12 HSN summary using the new dropdown HSN selector. Upload JSON, fix any portal validation errors, file with EVC. Total time: 60 minutes if you ran the cleanup checklist on September 8.
## Why this matters this week
The July 2025 GSTR-1 cycle was the first full month under the [hard-locked GSTR-3B Tables 3.1 and 3.2](https://cleartax.in/s/gst-return-filing-rule-changes-from-july-2025) — your GSTR-1 numbers now flow into GSTR-3B with zero edit room. A wrong invoice value in GSTR-1 is a wrong tax liability in GSTR-3B. The portal has rejected ITC for 12 of our supplier counterparties so far this quarter due to GSTR-1 mismatches that the seller did not catch on day one.
The September 11 due date is not the deadline you should plan for. The real deadline is September 8 — three days before — so you have a 72-hour window to reconcile portal errors without incurring the ₹50/day per return late fee.
## The 60-minute sprint (run this on September 8 or 9)
## What actually breaks (real failures from the August batch)
These are the actual portal errors we hit in the August 2025 batch, with the fix that worked.
## The pre-flight checklist
For a broader view of where we sit in the Indian tax-tech stack, our founder [Vivek Singh](https://viveksinra.com) writes on the same beat with a more first-person founder angle. Email us at contact@softechinfra.com if you want the GSTR-1 audit checklist sent before our call.
Sep 11
GSTR-1 due date for August 2025
60 min
Tally to filed return, no rework
4
Mistakes that trigger 90% of yellow flags
₹50/day
Late fee — capped at ₹5,000 per return
The GSTR-1 → GSTR-3B coupling is now hard. If your GSTR-1 has wrong B2B invoice values, your GSTR-3B Tables 3.1 and 3.2 inherit those errors with no edit option. The only correction route is GSTR-1A within the same tax period. Plan to file GSTR-1 by September 9 to leave time for a GSTR-1A correction before September 20.
## The 4 mistakes that triggered notices in 2025
B2B invoices missing from the IRN log
An e-invoice was generated on the IRP portal but never made it into Tally because the integration token expired mid-month. The invoice exists at GSTN; your books say it does not. GSTR-1 ships short. Buyer's GSTR-2B does not match. Notice arrives in 21 days.
HSN summary missing from Table 12
From January 2025 onwards, HSN codes must be selected from the GSTN dropdown — manual entry is rejected. We saw four clients ship JSON with 8-digit codes the dropdown does not recognise. The portal accepts the upload but flags it for review.
Credit notes filed against the wrong original invoice
Tally lets you reference any invoice number when raising a credit note. The portal does not — the credit note must reference an invoice that exists in your filed GSTR-1 history. Fix the reference at source, not in the JSON.
B2C-Large invoices (above ₹2.5 lakh) missing place-of-supply
B2C-L line items above ₹2.5 lakh need explicit place-of-supply (POS) state codes for inter-state. Tally exports these correctly only if the customer ledger has a state populated. Walk-in customers with blank state ledgers slip through.
1
Minutes 0-10: Reconcile IRN log against Tally invoices
Login to einvoice1.gst.gov.in. Go to Reports > Generated IRN. Filter for August 2025. Export to Excel. In Tally, open Display More Reports > Statutory Reports > GST > e-Invoice Reports. Cross-check the count and total invoice value. Any IRN missing from Tally needs to be voucher-entered before the next step.
2
Minutes 10-20: Validate HSN summary against the GSTN dropdown
In Tally Prime: Display More Reports > Statutory Reports > GST > GSTR-1 > Table 12 (HSN Summary). Open the GSTN portal in a second tab. Returns Dashboard > Prepare Online > Table 12 > "Enter HSN" dropdown. Cross-check every HSN code in your summary against the dropdown. Any unrecognised code must be replaced with the closest valid one — usually a 6-digit truncation works.
3
Minutes 20-30: Audit credit notes
In Tally: Display More Reports > Day Book > filter Voucher Type = Credit Note. For every CN, open the original invoice it references. Confirm the original invoice number, date, GSTIN of recipient, and tax amount match exactly. Pay special attention to credit notes that reference invoices from FY 2024-25 — most often, the original invoice number prefix is wrong.
4
Minutes 30-40: B2C-L state code audit
Tally: Display More Reports > Statutory Reports > GST > GSTR-1 > B2CL section. Filter for invoices above ₹2,50,000 — these must have a place of supply. Any row with blank POS comes from a walk-in customer ledger with no state. Fix the customer master, then re-pull the report.
5
Minutes 40-50: Generate JSON and upload
Tally: F11 > Statutory > Generate JSON for upload. Saves to your default export folder. Login to gst.gov.in. Returns Dashboard > GSTR-1 > "Prepare Offline" > Upload. Choose your JSON. Wait for the success message. If you get a "Processed with errors" status, click "Generate Summary" to see the line-by-line failure list.
6
Minutes 50-60: Preview and file with EVC
On the portal, Returns > GSTR-1 > "Preview Draft GSTR-1". Download the PDF and eyeball the totals. If they match your Tally summary, click "File Statement" > EVC. OTP to your registered mobile. Save the ARN. Done.
| Portal error message | Root cause | Fix in Tally |
|---|---|---|
| "Duplicate invoice number for the same financial year" | Same invoice number used in both prefixed and non-prefixed forms | Voucher class > "Restart numbering" set to "Yearly" with explicit prefix INV/2025-26/ |
| "HSN code not found in master" | 8-digit code not present in GSTN dropdown for your turnover band | Truncate to first 6 digits in Stock Item master, regenerate JSON |
| "Place of supply mandatory for B2CL above 2.5 lakh" | Customer ledger has no state populated | Customer master > GST Details > Place of Supply field, set state code |
| "Original invoice not found for credit note" | Credit note references an invoice from a prior period that was never filed in GSTR-1 | Re-issue the credit note referencing the actual filed invoice number |
| "GSTIN of recipient invalid" | Recipient changed GSTIN during the year, Tally still has old one | Update party master, re-export the affected invoices only |
- IRN log from einvoice1.gst.gov.in matches Tally e-invoice report by count and total value
- Every HSN in Table 12 verified against the GSTN dropdown
- Every credit note has a verified-existing original invoice reference
- Every B2C-L row above ₹2.5 lakh has a state code in place of supply
- Customer GSTINs in party master verified against the Aug e-invoice batch
- Tally invoice numbering is "Restart numbering: Yearly" with prefix INV/2025-26/
- JSON exported, uploaded, "Processed with errors" status investigated and cleared
- Draft preview PDF totals match your Tally GSTR-1 report
- EVC OTP arrived on registered mobile, ARN saved to your file system
- If running close to deadline, GSTR-1A path planned for any post-filing corrections
Want this Tally-to-portal workflow built into your accounting software?
We build the reconciliation, HSN validation, and JSON generation pipeline directly into Tally TDL or as a Zoho Books custom report — for SMBs filing 200 to 4,000 invoices a month. Typical engagement: 9 working days, ₹65k-₹1.4 lakh fixed scope. First call is with the engineer who would write your TDL or Deluge code.
Book a 30-min Workflow CallTags:
GSTR-1TallyGSTIndian SMBE-InvoicingComplianceCFO
