Reconcile your sales register, GSTR-1 and GSTR-3B with this step-by-step month-end GST checklist.
Why GSTR-1 and GSTR-3B must agree
GSTR-1 reports outward supplies at invoice and summary levels. GSTR-3B is the summary return used to report tax liability, input tax credit and payment. Reconciliation compares both with the books so that omissions, classification differences and unpaid tax can be investigated before filing.
Step-by-step monthly reconciliation
- Freeze the period. Export the sales register, credit/debit notes, advances, GSTR-1 or IFF data (where applicable), and the draft GSTR-3B for the same tax period.
- Compare taxable value. Tie outward taxable sales and zero-rated, exempt and nil-rated supplies from the register to the applicable GSTR-1 tables.
- Compare tax heads. Reconcile IGST, CGST, SGST/UTGST and cess separately, rather than only the combined total.
- Check debit and credit notes. Identify notes in the books not reported on the portal or assigned to another period.
- Check place of supply and tax rate. An inter-state versus intra-state classification error can shift IGST into CGST and SGST, even where the total tax appears unchanged.
- Review advances and adjustments. Apply the GST timing rules relevant to your supplies, including applicable services and advance adjustments.
- Review amendments. Distinguish current-period changes in GSTR-1A from corrections in later GSTR-1 periods and consider the relevant statutory deadlines.
- Reconcile books to GSTR-3B. Review any difference in output liability, reverse charge, ITC and actual tax paid.
- Approve and archive. Retain a signed difference statement, supporting invoices, explanatory notes and the filed returns.
Simple reconciliation format
| Particulars | Books | GSTR-1 | GSTR-3B | Action |
|---|---|---|---|---|
| Taxable outward supplies | As per register | As filed/draft | As reported | Investigate variances |
| IGST | Ledger | Supply details | Liability | Check interstate supplies |
| CGST and SGST | Ledgers | Supply details | Liability | Check state and rate |
| Credit/debit notes | Note register | Note tables | Tax adjustment | Check timing |
Example: missed sales invoice
Suppose a taxable sales invoice appears in the September books but not in the September GSTR-1 working. Determine whether GSTR-1 is still open, whether GSTR-1A can be used before filing the same-period GSTR-3B, or whether a correction is required through a later return. Check the tax liability separately. A later amendment is not a substitute for timely payment where tax was due earlier.
Common reconciliation errors
Missed B2B invoices, wrong GSTIN, duplicate invoices, wrong place of supply, omitted credit notes, timing differences, mismatched reverse-charge entries and inappropriate netting across tax heads are common investigation points.
Related GST and accounting guides
Start with the GST compliance pillar, review GST invoices and e-way bills, then review ITC reversals and your bank reconciliation controls. For filing delays see the GST late fee calculator.
Practical example and portal screenshots
Example: Books show ₹10,00,000 taxable outward supplies, GSTR-1 ₹9,90,000, and GSTR-3B ₹10,00,000. The ₹10,000 difference must be investigated invoice by invoice. In the workbook, enter these figures in the GSTR1 vs 3B sheet and investigate the REVIEW flags.
- Open GST Portal → Services → Returns → Returns Dashboard.
- Choose the filing period; download the GSTR-1 summary and review GSTR-3B details.
- Compare books, GSTR-1 and GSTR-3B tax-head totals in the Excel sheet.
- Record reasons for each mismatch and obtain review/approval before filing amendments.
Official illustrated screens: GST Portal guide showing GSTR-1 dashboard, download summary and invoice screenshots. These are official demonstration screens, not a live taxpayer account.
Download Free GST Reconciliation Excel Toolkit
Practice with editable example records and reconciliation formulas for GSTR-1 vs GSTR-3B, invoice/e-way bill checking, and ITC reversals. Replace illustrative data with your own working papers and review all exceptions before filing.
Download Excel Toolkit (.xlsx) ↓
For education and internal control work. Check current GST rules and verify return data independently.
Official reference
GST Portal: GSTR-1 and GSTR-1A taxpayer FAQ. Filing dates and correction processes may change under notifications or advisories.
Last reviewed: 28 September 2026 · By TaxNexus Editorial Team · Educational information; check current GST notifications and consult a qualified professional for transaction-specific advice.
