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The sales ledger total for the month does not equal the taxable value in GSTR-3B Table 3.1, and the accountant cannot tell whether the return or the books are wrong.
List every cause that moves one side but not the other: timing of invoices, credit notes, advances already taxed, exports in a separate row, exempt sales, reverse-charge entries and unposted corrections.
A one-page monthly bridge starting from the sales ledger total, with one line per cause and a closing figure that must equal GSTR-3B Table 3.1.
A bridge where the unexplained difference is zero, plus a list of items to correct in books, in GSTR-1A or in next month's GSTR-1.
Your GSTR-3B sales will often differ from your sales books in a given month, and that is usually not an error. The gap almost always comes from timing, credit notes, advances, exports, exempt sales, reverse-charge entries or a correction that has been made on one side but not the other. The fix is a short monthly bridge that explains every rupee.
Why do the two figures differ at all?
GSTR-3B Table 3.1 is built from what you report in GSTR-1 (and GSTR-1A). Your sales ledger is built from what you post in Tally, Zoho Books or your ERP. These are two separate records of the same sales, so anything recorded in one but not yet in the other shows up as a gap.
From the July 2025 tax period, the outward liability that the portal pre-fills into GSTR-3B is locked. You can no longer type over it. If the pre-filled figure is wrong, you correct it through GSTR-1A for the same month before filing GSTR-3B. That makes the GSTR-1 to books check even more important.
What are the likely causes?
| Cause | Which side is higher | Where to check | Fix |
|---|---|---|---|
| Invoice booked this month, reported in GSTR-1 next month | Books | Sales register date vs GSTR-1 filing | Report in next GSTR-1; note as timing |
| Credit note in GSTR-1 but not posted in books | Books | GSTR-1 Table 9B vs credit note ledger | Post the credit note in books |
| Advance already taxed, now adjusted against invoice | Books | GSTR-1 Table 11B | Bridge line; no correction needed |
| Export sale shown in row 3.1(b), not 3.1(a) | Books, if you compare 3.1(a) only | Table 3.1(b) | Compare the total of all rows |
| Exempt or nil-rated sales in row 3.1(c) | Books, if you compare 3.1(a) only | Table 3.1(c) | Compare the total of all rows |
| Reverse-charge purchases in row 3.1(d) | Return | Table 3.1(d) | Exclude from the sales comparison |
| Invoice cancelled in books, still in GSTR-1 | Return | GSTR-1 invoice list | Amend in GSTR-1A or next GSTR-1 |
Which books figure should I compare: sales ledger, sales register or trial balance?
Use the sales register (the invoice-level list) as your main figure. The trial balance sales account often includes items that are not GST supplies, such as discounts posted as expenses or other income heads. The sales register is closest to what GSTR-1 contains, invoice by invoice. Then tie the register total to the trial balance as a separate check.
How do I handle differences carried over from earlier months?
Keep a running list. A timing difference this month should reverse next month. Each month:
- Start with last month’s open items.
- Tick off the ones that reversed.
- Add this month’s new items.
- Investigate any item older than two months, because it is probably a real error rather than timing.
Under Section 39(9) of the CGST Act, 2017, corrections to an earlier month are made in a later return, with interest at 18 percent under Section 50 on any tax paid late.
Worked example
Your sales register for September shows taxable sales of ₹48,60,000. GSTR-3B Table 3.1(a) shows ₹47,25,000. The gap is ₹1,35,000.
| Line | Amount |
|---|---|
| Sales register taxable value | ₹48,60,000 |
| Less: credit note reported in GSTR-1, not yet posted in books | ₹90,000 |
| Less: advance taxed in August, adjusted against a September invoice | ₹30,000 |
| Less: export sale shown in row 3.1(b) | ₹15,000 |
| Equals GSTR-3B Table 3.1(a) | ₹47,25,000 |
Check: ₹90,000 + ₹30,000 + ₹15,000 = ₹1,35,000, and ₹48,60,000 minus ₹1,35,000 = ₹47,25,000. Only the credit note needs action: post it in the books. The advance and the export are explained differences, not errors. At 18 percent, the credit note alone carries ₹16,200 of GST, which is why it is worth chasing.
What to read next
- Next in this series: Why is the ITC in my books different from the ITC in GSTR-3B?
- The month-end tie-out before filing: GSTR-1 vs GSTR-3B runbook for days 16 to 20
- The year-end version: Why does my GSTR-9 not match my books?
- How the matching works at volume: GST reconciliation software
GSTR-1 and GSTR-3B matching leads the TransactIG GST roadmap; today TransactIG reconciles bank statements to the books and TDS.
Content authored by practitioners with experience at Amazon India, Intuit QuickBooks, and the Tata Group. Meet the team →