GSTR-1 Filing Services — Outward Supply Reporting for GST Compliance
Monthly and quarterly GSTR-1 filing with GSTIN validation, HSN mapping, e-Invoice integration and pre-filing GSTR-3B reconciliation
GSTR-1 — The Foundation of GST Compliance
GSTR-1 is the foundational return in India's GST compliance system — the monthly or quarterly statement of outward taxable supplies filed by every GST-registered taxpayer. It declares every invoice issued during the period: B2B invoices (to registered buyers), B2C large invoices (to unregistered buyers above ₹2.5 lakh), exports, credit notes, debit notes, advances received, and nil-rated or exempt supplies. The data filed in GSTR-1 by a supplier is automatically reflected in the GSTR-2A and GSTR-2B of the recipient — making accurate GSTR-1 filing a direct service to your customers' input tax credit.
At N D Savla & Associates, our GST team in Mumbai provides expert GSTR-1 filing services for businesses across all industries. We extract invoice data from your accounting system, classify supplies correctly by return category, validate GST registration numbers (GSTINs) of buyers, map HSN/SAC codes at the invoice level, and file GSTR-1 on the GSTN portal within the statutory deadline. Our filing process includes a pre-submission reconciliation with your books — ensuring the return reflects reality and minimises downstream GSTR-2B mismatches for your buyers.
GSTR-1 accuracy is a double obligation — it protects both your own compliance record and your customers' ITC. A GSTR-1 filed late or with errors means your buyer's GSTR-2B won't reflect the purchase, blocking their ITC until the error is corrected. In an ecosystem where ITC drives working capital, GSTR-1 accuracy is a business relationship responsibility as much as a tax compliance requirement.
Who Must File GSTR-1, and How Often?
GSTR-1 is mandated under Section 37 of the CGST Act, 2017. Every registered person — other than composition dealers, non-resident taxable persons, input service distributors, persons under Section 51 or 52, and certain other categories — must file GSTR-1 for each tax period. Regular taxpayers with annual aggregate turnover above ₹5 crore must file GSTR-1 monthly, by the 11th of the following month. Taxpayers up to ₹5 crore turnover can opt for the QRMP scheme — filing GSTR-1 quarterly, by the 13th of the month following the quarter, with the option to use the Invoice Furnishing Facility (IFF) to upload B2B invoices in the first two months of each quarter.
Structure of GSTR-1: Tables and What Goes Where
Table 4 — B2B Supplies (Invoice-Level)
All B2B taxable supplies to registered buyers are reported invoice-by-invoice — buyer's GSTIN, invoice number, date, value, place of supply, tax rate, and tax amount. This is the most critical table: errors here directly block the buyer's ITC. We validate every GSTIN against the GSTN registry before filing.
Table 5 — B2C Large Supplies
B2C invoices above ₹2.5 lakh to unregistered buyers in a different state (inter-state) are reported individually with state-wise place of supply. This facilitates the GST department's tracking of large inter-state B2C transactions.
Table 6 — Zero-Rated Supplies (Exports and SEZ)
All export invoices, with or without payment of IGST, and supplies to SEZ units or developers are reported here. For exporters claiming IGST refunds, accurate Table 6 reporting is the starting point of the refund chain. We coordinate export entries with shipping bills for integrated customs-GST reconciliation.
Tables 7 and 8 — B2C Small and Nil/Exempt
Small B2C supplies (intra-state and inter-state below ₹2.5 lakh) are reported as consolidated state-wise figures in Table 7. Nil-rated, exempt, and non-GST outward supplies go in Table 8 — essential for businesses dealing in both taxable and exempt supplies, such as hospitals, educational institutions, and mixed supply businesses.
Tables 9 and 10 — Amendments
Invoices from prior months that need correction are reported in Table 9 (B2B amendments) and Table 10 (B2C amendments). Amendments update the recipients' GSTR-2A and GSTR-2B accordingly. We track all invoice amendments systematically so prior-period corrections are captured correctly.
Table 11 — Advances Received
GST is payable on advances received against future supplies for which invoices are not yet issued. Once the invoice is issued, the advance is adjusted in Table 11 in a subsequent month. Managing advance tax payment and adjustment is a common compliance gap that our team manages rigorously.
Tables 12 and 13 — HSN Summary
GSTR-1 requires an HSN-wise breakup of outward supplies. We map every product and service to the correct HSN/SAC code as part of GSTR-1 preparation, at the digit level required for your turnover band.
HSN Reporting Thresholds
| Annual Aggregate Turnover | HSN Digit Level Required | What This Means in Practice |
|---|---|---|
| Above ₹5 crore | 6-digit HSN | Product master must be mapped to 6-digit precision across every SKU |
| ₹1.5 crore to ₹5 crore | 4-digit HSN | Broader classification, but consistency across periods still matters |
| Below ₹1.5 crore | 2-digit HSN | Summary-level reporting, mapped from the same product master |
Historical Context: The Evolution of Outward Supply Reporting
The concept of outward supply reporting in Indian indirect tax predates GST. Under the Central Excise regime, manufacturers filed ER-1 returns declaring production and clearances — the excise duty equivalent of GSTR-1. Service tax required ST-3 returns declaring services rendered and tax collected. VAT returns under state laws required B-form declarations of sales. Each was a siloed, paper-intensive process with no cross-verification between systems.
GST's GSTR-1 was designed to be transformatively different — a digital, invoice-level, real-time reporting system that would create a unified picture of India's supply chain. The original GSTR-1/GSTR-2/GSTR-3 system envisaged automated matching of every supplier's GSTR-1 invoice with the recipient's GSTR-2 purchase record — a system-driven ITC validation that would eliminate fake invoice fraud. This matching system proved technically unworkable at scale in 2017 and was suspended.
Key Milestones Shaping GSTR-1
| Period | Development | Effect on GSTR-1 Filing |
|---|---|---|
| Pre-GST | ER-1, ST-3 and state VAT returns | Siloed, paper-intensive reporting with no cross-verification |
| 2017 | GSTR-1/2/3 matching system suspended | GSTR-1 continues; automated invoice matching abandoned |
| October 2020 | E-Invoice mandatory above ₹500 crore | B2B invoice data begins auto-populating into GSTR-1 Table 4 |
| 2021 | E-Invoice extended above ₹10 crore | Manual data entry eliminated for a much wider taxpayer base |
| January 2021 | QRMP scheme with monthly IFF | Quarterly GSTR-1 for small taxpayers, ITC flow preserved via IFF |
| August 2023 | E-Invoice extended above ₹5 crore | Auto-population becomes the norm for most B2B suppliers |
For exporters, integration between ICEGATE (Customs) and GSTN for shipping bill data in GSTR-1 Table 6 further automated reporting. The QRMP scheme reduced the return filing burden for over 94% of GST taxpayers while preserving ITC flow to their customers. Our advisory includes QRMP eligibility assessment and optimal IFF usage planning for eligible clients — as part of the wider GST return filing cycle.
Our GSTR-1 Filing Process: Step by Step
Invoice Data Collection and Validation
We collect the sales register from your accounting system for the filing period. Every invoice is validated for the buyer's GSTIN (checked against the GSTN registry), correct invoice number (sequential, no duplicates), place of supply (correct state code based on the buyer's GSTIN or delivery address), HSN/SAC code and description, tax rate, and invoice value. Validation errors are flagged and resolved before filing.
Classification by GSTR-1 Table
Invoices are classified into GSTR-1 tables: B2B (Table 4), B2C large (Table 5), exports (Table 6), B2C small (Table 7), nil/exempt (Table 8), advances (Table 11), and amendments (Tables 9 and 10). This classification directly determines which buyer gets which ITC credit — misclassifying a B2B supply as B2C causes ITC loss for the buyer.
HSN Summary Preparation
HSN-wise totals are computed at the required digit level based on the taxpayer's turnover. For multi-product businesses, HSN mapping requires product master maintenance — which we manage as part of the filing service.
Pre-Filing Reconciliation
Before uploading to GSTN, we reconcile the GSTR-1 data against the GSTR-3B summary filed for the same period, or to be filed — ensuring outward supply totals are consistent, since mismatches attract ASMT-10 notices. We also cross-check against the previous GSTR-1 for any prior-period invoices requiring amendment. For comprehensive cross-return reconciliation, see our GSTR-2A Reconciliation and GSTR-2B Reconciliation services.
GSTN Portal Upload and Filing
Validated data is uploaded to the GSTN portal using JSON upload for large volumes, or direct portal entry for smaller volumes. After upload, we review the portal-generated summary, confirm all figures, and file GSTR-1 using the authorised signatory's Digital Signature Certificate (DSC) or EVC (Electronic Verification Code).
Confirmation and Archiving
After filing, the GSTR-1 acknowledgment (ARN — Acknowledgment Reference Number) is downloaded and archived, along with the GSTR-1 preview PDF as a permanent record. Any IFF filings made during the quarter are reconciled against the quarterly GSTR-1 to ensure all B2B invoices are correctly included.
GSTR-1 Amendments: Correcting Past Errors
A GSTR-1 filed in a prior month can be amended in the current month's GSTR-1 using the amendment tables — Tables 9A, 9B and 9C for B2B, and Table 10 for B2C. Common amendments include correcting a buyer's GSTIN, changing invoice value or tax rate, adding a missed invoice, or cancelling a reported invoice that was not actually issued. Each amendment updates the recipient's GSTR-2B and can restore blocked ITC.
We track all pending amendments systematically. Note that amendments can only go back to the current financial year — prior year amendments require reversal and fresh reporting. For disputed ITC situations arising from GSTR-1 errors, our GST Appeal Services provide recovery support.
Why Choose N D Savla & Associates for GSTR-1 Filing in Mumbai?
GSTIN Validation on Every Invoice
We validate every buyer's GSTIN against the GSTN registry before filing — eliminating invalid GSTIN errors that can block ITC for your customers.
HSN Code Management
We maintain a product-service HSN/SAC master for each client, ensuring every supply is correctly classified and HSN summaries at the required digit level are always accurate.
E-Invoice Integration
For clients on e-Invoice, we integrate IRP (Invoice Registration Portal) data directly into GSTR-1, eliminating double-entry and ensuring e-Invoice and GSTR-1 are always consistent.
Pre-Filing GSTR-3B Consistency Check
Every GSTR-1 we file is cross-checked against the corresponding GSTR-3B for outward supply consistency — preventing the mismatch notices that commonly follow uncoordinated filings. Combined with our GST Return Filing service, this creates a seamless monthly compliance cycle.
IFF Advisory for QRMP Clients
We advise QRMP-eligible clients on optimal IFF usage — ensuring key B2B customers receive ITC credits in the first two months of each quarter without waiting for the quarterly GSTR-1.
Export and SEZ Reporting
Export entries in Table 6 are coordinated with shipping bills so the customs-GST chain reconciles — the starting point for any IGST refund claim on zero-rated supplies.
GSTR-1 sits at the front of the monthly cycle. It feeds directly into GSTR-2A reconciliation and GSTR-2B reconciliation for your buyers, and works alongside ITC-04 job work filing where deemed supplies arise. For income tax obligations that run alongside your GST compliance, see TDS Return Filing and TDS on Purchase of Property.
Why GSTR-1 Accuracy Is a Commercial Issue, Not Just a Tax One
- Your buyer's GSTR-2B is built from your GSTR-1 — a missed invoice blocks their ITC
- Blocked ITC ties up your customer's working capital, straining the relationship
- A misclassified B2B supply reported as B2C removes the buyer's credit entirely
- Late GSTR-1 blocks your own GSTR-3B filing from January 2022 onwards
- Wrong GSTINs send credit to a third party and require Table 9A amendment to unwind
- Consistent, on-time filing makes you a supplier that buyers prefer to keep
Frequently Asked Questions — GSTR-1 Filing
What is the due date for GSTR-1?
Monthly filers with turnover above ₹5 crore file by the 11th of the following month. QRMP quarterly filers file by the 13th of the month following the quarter — the April to June quarter is due 13 July, July to September due 13 October, and so on. IFF uploads under QRMP are due by the 13th of each of the first two months of the quarter.
What is the late fee for not filing GSTR-1?
Late fee for GSTR-1 is ₹200 per day (₹100 CGST + ₹100 SGST), capped at ₹10,000 per return for taxpayers with taxable supply. For taxpayers with nil outward supplies, the cap is ₹500 per return. From January 2022, a system-level restriction prevents filing GSTR-3B if GSTR-1 for the same period is not filed, making GSTR-1 non-filing a double blockage.
Can a buyer claim ITC if the supplier has not filed GSTR-1?
No. ITC in GSTR-2B is auto-populated only from suppliers who have filed their GSTR-1. If a supplier misses GSTR-1 or omits an invoice, the buyer's GSTR-2B will not show that purchase, and ITC will be blocked. This is why choosing a supplier who files timely GSTR-1 is a commercial, not just a compliance, consideration. Our GSTR-2B Reconciliation service tracks missing supplier GSTR-1 filings and enables timely follow-up.
Are e-Invoices automatically uploaded to GSTR-1?
Yes, for taxpayers covered by e-Invoice. B2B invoices with a valid IRN (Invoice Reference Number) from the IRP are auto-populated in GSTR-1 Table 4. Only B2C invoices, credit notes without IRN, and certain exempt supply invoices still require manual entry. E-Invoice auto-population significantly reduces GSTR-1 preparation time for covered taxpayers. For TDS obligations on payments to contractors, service providers, and property transactions that intersect with business accounting, see our TDS Return Filing and TDS on Purchase of Property services.
What is the consequence of reporting a wrong GSTIN in GSTR-1?
If a wrong GSTIN — non-existent, or the wrong party's — is reported in GSTR-1, the ITC will be credited to the wrong party's GSTR-2B, or no ITC will flow if the GSTIN does not exist. The correct approach is to amend GSTR-1 in the following month using Table 9A to cancel the wrong entry and Table 4 to re-enter with the correct GSTIN.
File GSTR-1 Accurately, Every Period
Monthly and quarterly GSTR-1 filing with GSTIN validation, HSN mapping, IFF advisory and pre-filing reconciliation — for businesses across Mumbai, Thane, Navi Mumbai, Pune and pan-India.
- 📞 +91 98218 32683 | WhatsApp +91 98190 00511
- ✉ nainitsavla@savlagroup.in
- 📍 Suite No. 102, L1, Ashok Premises, Nicholas Road, Andheri East, Mumbai 400069
- 🕐 Monday–Saturday | 10:00 AM – 7:00 PM