Direct Answer: In GSTR-2B reconciliation, ₹1 to ₹2 differences in IGST, CGST, or SGST are legitimate computational variances caused by divergent rounding algorithms (item-level rounding vs. invoice-level rounding) between your ERP and your supplier's billing system. Under Section 170 of the CGST Act, amounts of tax, interest, and penalties must be rounded off to the nearest rupee (50 paise or more rounded up, less than 50 paise disregarded). To resolve these discrepancies, apply a ±₹1.00 tolerance per tax component during reconciliation, claim no more credit than GSTR-2B shows, and post the fractional difference to a "GST Round-Off Ledger" in your books.
For the other causes of a GSTR-2B mismatch and how to fix each one, see our guide to common reconciliation errors.
Every month, finance teams waste dozens of hours chasing suppliers over 48 paise or 1-rupee differences on 500+ invoices. When rigid Excel VLOOKUP formulas compare exact numeric strings, an invoice with ₹1,850.40 tax in Tally fails to match a GSTR-2B entry of ₹1,850.00, falsely tagging legitimate vendor bills as mismatched. The tool uses one cleaned key (GSTIN + cleaned invoice number) and a ₹1 tax tolerance. It cannot read your IMS dashboard: an invoice missing from GSTR-2B whose supplier has other invoices there is flagged as likely IMS Pending, for you to check.
This technical breakdown explains the mathematics behind decimal variances, details the statutory backing under Section 170, and shows how to automate tolerance matching without manual ledger corrections.
Why 1-rupee differences happen: the math explained
A round-off variance is rarely a tax evasion attempt or a commercial pricing dispute. It is almost always an artifact of where and when the decimal rounding occurs in the software pipeline:
1. Item-level vs. invoice-level rounding
Consider an invoice with 5 line items, each having a taxable value of ₹105.30 at 18% IGST:
- Supplier Software (Item-Level Rounding):
Line 1 Tax: ₹105.30 × 18% = ₹18.954 → rounded to ₹18.95
5 items × ₹18.95 = Total Tax Billed: ₹94.75. - Buyer ERP (Invoice-Level Rounding):
Total Taxable Value: 5 × ₹105.30 = ₹526.50
Total Tax: ₹526.50 × 18% = ₹94.77.
Rounding each line to the paisa leaves a gap of only 2 paise here. The gap grows when a billing tool rounds each line to the whole rupee: ₹18.954 becomes ₹19 per line, so five lines give ₹95.00 against ₹94.77, and an invoice with many lines can drift by a rupee or more against a total calculated once.
2. Independent rounding of CGST and SGST
In intra-state supplies, tax is split equally into Central Tax (CGST) and State Tax (SGST):
- If an item carries a taxable value of ₹155.00 at 18% GST (9% CGST + 9% SGST):
- CGST = ₹155.00 × 9% = ₹13.95
- SGST = ₹155.00 × 9% = ₹13.95
- If one system rounds each head to the whole rupee, it shows ₹14.00 + ₹14.00 = ₹28.00. Another keeps paise and shows ₹13.95 + ₹13.95 = ₹27.90. The gap is 5 paise per head and 10 paise in total, and across many lines it can add up to a rupee or more.
The statutory framework: Section 170 of the CGST Act, 2017
Many junior accountants fear that claiming an invoice with a 1-rupee difference will trigger a GST audit notice. Section 170 of the CGST Act explicitly provides the statutory standard for rounding:
“Section 170. Rounding off of tax, etc. The amount of tax, interest, penalty, fine or any other sum payable, and the amount of refund or any other sum due, under the provisions of this Act shall be rounded off to the nearest rupee and, for this purpose, where such amount contains a part of a rupee consisting of paise, then, if such part is fifty paise or more, it shall be increased to one rupee and if such part is less than fifty paise it shall be ignored.”
Central Goods and Services Tax Act, 2017
Section 170 covers the rounding of amounts payable and refunds. It does not set a tolerance for comparing your books with GSTR-2B: the ±₹1.00 used by our tool is a screening threshold, not a legal allowance.
A separate rule matters for larger gaps. Under Rule 88D, if the ITC you claim in GSTR-3B exceeds the ITC available in GSTR-2B by more than a pre-defined limit, you receive an intimation in Form DRC-01C, and you must pay the excess ITC or explain the reasons within seven days (GSTN advisory on DRC-01C; Notification 38/2023-Central Tax). We do not quote the limit here; check the current GSTN advisory. For how to respond, see how to reply to a DRC-01C notice.
Comparative analysis: 3 ways businesses handle round-off differences
| Method | How It Works | Operational Burden | Compliance & Audit Risk |
|---|---|---|---|
| 1. Exact Formula Matching (No Tolerance) | VLOOKUP requires exact decimal match. Any 50-paise difference is marked "Unmatched". | Extremely high: Accountants waste hours checking minor discrepancies manually. | Zero tax risk, but massive administrative waste and delayed return filing. |
| 2. Manual Editing of Purchase Vouchers | Accountant modifies Tally/ERP purchase vouchers to match GSTR-2B decimal values exactly. | High: Breaks reconciliation with the physical vendor invoice and payment ledger. | High risk: Auditor queries why ERP voucher amount diverges from physical paper bill. |
| 3. Tolerance Matching (±₹1) with Round-Off Ledger | System matches invoices when the total tax and each tax head are within ±₹1.00. Net difference posted to expense round-off ledger. | Minimal: small rounding differences are cleared automatically, so you review only the real exceptions. | Clean: the voucher still matches the physical invoice, and larger differences stay visible as mismatches. |
Standard accounting entry for GST round-off differences
When booking purchase bills where the physical invoice tax differs by a few paise from your ERP calculation or GSTR-2B, use a designated indirect expense ledger:
This ensures your vendor ledger matches the bank payout to the rupee, your Input Tax Credit ledger matches GSTR-2B exactly, and the fractional variance is absorbed cleanly into standard financial round-off accounts.
How deterministic tolerance matching works in GSTR2BMatch
Traditional Excel formulas (VLOOKUP or INDEX/MATCH) fail when numbers differ by even ₹0.01. The reconciliation engine inside gstr2bmatch.in applies a multi-tier matching algorithm:
- Clean Key Matching: Identifies invoices by normalized Supplier GSTIN and Invoice Number (stripping special characters and leading zeros).
- Value Check with a ±₹1.00 tolerance per head: Compares the total tax of the invoice, then each tax head (IGST, CGST, SGST and cess) on its own. If the total and every head are within ±₹1.00, the invoice is Matched (bucket A) rather than an error. The taxable value is not compared. If your purchase register has only a total tax column, the tool compares the total alone.
- Audit Trail Isolation: An invoice whose total differs by more than ₹1.00 goes to Value mismatch with the reason “Tax amount mismatch”. If the total agrees but a head differs by more than ₹1.00, it also goes to Value mismatch, for example with the reason “Tax head mismatch (IGST vs CGST+SGST)”. Real discrepancies stay apart from harmless rounding.
Note that the tolerance applies to each figure separately. A difference of ₹0.60 in CGST and ₹0.60 in SGST is within ₹1.00 on each head, but the total differs by ₹1.20, so the invoice is a value mismatch.
Stop wasting time on 50-paise inconsistencies
Eliminate false mismatches in seconds. Drop your purchase register and official GSTR-2B file into our browser tool to match your vouchers with a built-in ₹1.00 tolerance on the total tax and on each tax head. Your GSTR-2B and purchase register files are read in your browser and never uploaded to any server.
Reconcile GSTR-2B →Frequently asked questions
Will a ₹1 tax difference trigger a notice under Rule 88D (DRC-01C)?
A ₹1 difference on one invoice is not what decides it. Form DRC-01C is an intimation you receive when the ITC claimed in GSTR-3B exceeds the ITC available in GSTR-2B by more than a pre-defined limit. You must then pay the excess or explain the reasons within seven days. We do not quote the limit here; check the current GSTN advisory. Claiming no more than GSTR-2B shows keeps rounding differences from adding to the gap.
Should I claim ITC as per the physical invoice or as per GSTR-2B?
Under Section 16(2)(aa) of the CGST Act, Input Tax Credit can only be claimed if the details of the invoice have been furnished by the supplier in GSTR-1 and communicated to the recipient in GSTR-2B. Therefore, you should never claim more credit than what is reflected in GSTR-2B. If GSTR-2B is lower by ₹1, claim the GSTR-2B figure and write off the rupee difference.
Does GSTR2BMatch allow adjusting the rounding tolerance?
No. The tolerance is fixed at ±₹1.00 and there is no setting to change it. The tool applies it to the total tax and to each tax head (IGST, CGST, SGST and cess), when your register has head columns. This ensures decimal rounding differences between different ERP engines (like Tally, Busy, and Zoho) do not break reconciliation, while preventing larger mismatched values from slipping through.
Related guides
- GSTR-2B mismatch: common reconciliation errors and how to fix each one
- GSTR-2B invoice number mismatch: leading zeros, slashes and special characters
- how to find GSTR-2B mismatches: finding them in three passes: totals, supplier, invoice
Last checked: 21 October 2026. Sources: Section 170, CGST Act, GSTN advisory on DRC-01C, Rule 88D, CGST Rules (inserted by Notification 38/2023-Central Tax).