Key Takeaways on GST Return Mismatch
- A GSTR-1 vs GSTR-3B mismatch occurs when outward supplies reported in GSTR-1 do not match the tax liability declared in GSTR-3B for the same tax period
- From the July 2025 tax period, the liability in GSTR-3B Table 3 is auto-populated from GSTR-1/GSTR-1A and cannot be edited (GSTN advisory, June 2025), so outward-supply errors must be corrected in GSTR-1A before GSTR-3B is filed
- ITC mismatches above the limit set on the portal trigger a system-generated DRC-01C intimation (Rule 88D) after GSTR-3B is filed
- Reconciliation sequence: Books → GSTR-1 → GSTR-3B → GSTR-2B → E-invoice → E-way bill
- Invoice Management System (IMS) has been live since October 2024 and is optional: invoices you take no action on are deemed accepted and flow into GSTR-2B
How do I fix a GSTR-1 vs GSTR-3B mismatch? Follow the reconciliation sequence: Books → GSTR-1 → GSTR-3B → GSTR-2B. Compare totals at each step. If difference exceeds GST portal limits, you'll receive a DRC-01B notice. Respond within 7 days by paying the difference via DRC-03 or providing explanation in Part B.
You filed GST returns. System generated a mismatch notice. Tax officer asking for reconciliation. GST return mismatches are one of the most common triggers for scrutiny notices, tax demands, and compliance headaches.
With GSTR-3B Table 3 now locked to GSTR-1/GSTR-1A, liability mismatches have to be fixed at the GSTR-1 stage. The portal also compares GSTR-1 with GSTR-3B (Rule 88C) and GSTR-3B ITC with GSTR-2B (Rule 88D), and officers use e-invoice and e-way bill data in scrutiny.
This guide provides complete framework for identifying and fixing GST return mismatches. from Books through GSTR-1, GSTR-3B, GSTR-2B, e-invoice, to e-way bill.
Why GST Return Mismatches Happen
GST return mismatches occur when difference exists between what you report in one return and what appears in another. or between returns and books of accounts.
Common Causes Across All Mismatches
| Cause | Description |
|---|---|
| Timing Differences | Invoices reported in later GSTR-1 period than when liability paid in GSTR-3B |
| Data Entry Errors | Manual errors in invoice values, GSTINs, or tax rates |
| Duplicate Reporting | Same invoice entered twice in GSTR-1 |
| Period Mismatches | Reporting transactions in wrong tax period |
| Omissions | Forgetting to report invoices, debit notes, or credit notes |
| Classification Errors | Incorrect HSN/SAC codes or tax rate application |
| Amendment Limitations | Inability to amend certain errors in earlier GST years |
Reconciliation Flow: Books → GSTR-1 → GSTR-3B → GSTR-2B → E-invoice → E-way bill
Effective GST reconciliation follows specific sequence. Each step checks different type of mismatch:
| Step | Comparison | What It Checks |
|---|---|---|
| 1 | Books → GSTR-1 | Are all sales recorded in books reported in GSTR-1? |
| 2 | GSTR-1 → GSTR-3B | Does tax liability in GSTR-3B match supplies reported in GSTR-1? |
| 3 | Books → GSTR-3B | Is tax paid in GSTR-3B consistent with books? |
| 4 | GSTR-2B → GSTR-3B | Is ITC claimed in GSTR-3B supported by GSTR-2B? |
| 5 | Books → GSTR-2B | Is ITC recorded in books matching GSTR-2B? |
| 6 | E-invoice → GSTR-1 | Do e-invoices align with GSTR-1 B2B supplies? |
| 7 | E-way bill → GSTR-1 | Do e-way bills match GSTR-1 outward supplies? |
1. Books vs GSTR-1: Missing or Incorrect Outward Supplies
The Problem: Books show sales not reported in GSTR-1. or GSTR-1 shows sales not in books.
This is the first mismatch point in the reconciliation chain. If outward supplies in your books don't match GSTR-1, downstream mismatches in GSTR-3B and GSTR-2B are inevitable. See our complete GSTR-1 filing guide for step-by-step return preparation.
Common Causes
| Issue | Description |
|---|---|
| Invoice Omitted | Sales invoice recorded in books but not uploaded in GSTR-1 |
| Invoice Missed in GSTR-1 | Sales invoice missed during GSTR-1 filing |
| GSTIN Error | Wrong GSTIN entered for B2B invoice |
| HSN/SAC Error | Incorrect HSN/SAC code used |
| Value Mismatch | Taxable value in GSTR-1 differs from books |
| Debit/Credit Notes Omitted | Debit/credit notes not reported in GSTR-1 |
How to Fix
- Reconcile invoice-level data from GSTR-1 with sales register
- Identify invoices in books without corresponding GSTR-1 entry
- Identify invoices in GSTR-1 not in books
- Correct omissions by reporting missing invoices in next GSTR-1
- Correct errors by filing amendments
When to Act
Before filing each GSTR-1, reconcile with sales register, e-invoice data, e-way bill data, and debit notes
2. GSTR-1 vs GSTR-3B: Tax Liability Mismatch
The Problem: Tax liability declared in GSTR-3B does not match outward supplies reported in GSTR-1.
This is most common trigger for GST scrutiny notices. Portal's automated reconciliation system checks difference between liability declared in GSTR-1 and liability paid in GSTR-3B.
Common Mismatch Scenarios
| Scenario | Problem | Reason | Solution |
|---|---|---|---|
| GSTR-1 > GSTR-3B | GSTR-1 shows higher supplies than GSTR-3B liability | Tax liability missed in GSTR-3B | Reconcile & correct GSTR-3B; pay additional tax if needed |
| GSTR-3B > GSTR-1 | GSTR-3B liability higher than GSTR-1 supplies | Excess payment or reporting differences | Reconcile; check for duplicates |
| General Mismatch | GSTR-1 ≠ GSTR-3B | Timing differences, credit notes, advances | Prepare reconciliation statement |
| HSN Summary Mismatch | HSN-wise supplies don't match GSTR-3B | Classification errors | Verify HSN/SAC codes and rates |
Common Causes
| Cause | Explanation |
|---|---|
| Timing Differences | Invoices reported in later GSTR-1 period than liability paid in GSTR-3B |
| Credit Notes After Cut-off | Credit notes issued after Section 34(2) cut-off date |
| Debit Notes and Advances | Reporting and adjustment of advances and debit notes |
| Amendment Limitations | Inability to amend certain errors from earlier GST years |
| E-invoicing Data Flow | IRN data not flowing correctly from e-invoice to GSTR-1 |
| Duplicate Reporting | Same invoice reported twice in GSTR-1 |
| Omission | Invoice omitted from GSTR-1 or GSTR-3B |
How to Fix
Step 1: Identify the Difference
Download GSTR-1 and GSTR-3B for relevant period. Compare total outward supplies and tax liability.
Step 2: Prepare Reconciliation Statement
For each difference, explain reason:
- Timing difference (invoice in GSTR-1, liability in next GSTR-3B)
- Credit/debit note adjustments
- Advance adjustments
- Data entry errors
Step 3: Correct the Return
- If GSTR-1 correct but GSTR-3B wrong: GSTR-3B cannot be revised. Pay the short-paid tax in the next GSTR-3B or through DRC-03, with interest at 18% per annum under Section 50
- If GSTR-1 wrong: correct it through GSTR-1A before filing that month's GSTR-3B, or amend it in a later GSTR-1 (within the time allowed for amendments)
Step 4: Respond to Notices
If you receive ASMT-10 scrutiny notice, reply using Form ASMT-11 with reconciliation statement.
What Happens If You Ignore It
If the GSTR-1 liability exceeds the GSTR-3B liability by more than the notified limit, the portal issues DRC-01B (Rule 88C). Within 7 days, pay the difference through DRC-03 or explain it in Part B of DRC-01B. Until you respond, GSTR-1/IFF for the next period is blocked. See how to reply to DRC-01B and DRC-01C notices.
3. GSTR-2B vs GSTR-3B: ITC Mismatch
The Problem: Input Tax Credit (ITC) claimed in GSTR-3B does not match ITC available in GSTR-2B.
ITC Mismatch Scenarios
| Scenario | Problem | Reason | Solution |
|---|---|---|---|
| ITC Claimed > GSTR-2B | More ITC claimed than in GSTR-2B | Supplier has not filed GSTR-1 | Verify IMS/2B; follow up with supplier |
| ITC Available < GSTR-3B | GSTR-2B shows less than claimed | Supplier mismatch or delay | Check supplier compliance; reverse if ineligible |
| ITC in Books > GSTR-2B | Books show more than GSTR-2B | Invoice not uploaded by supplier | Follow up with supplier |
| ITC in GSTR-2B not Claimed | GSTR-2B shows ITC not claimed | Missed ITC claim | Claim in a later GSTR-3B within the Section 16(4) limit (30 November after the financial year, or the annual return if earlier) |
Key 2026 Changes
1. GSTR-3B Liability Lock
From the July 2025 tax period, GSTR-3B Table 3 liability is auto-populated from GSTR-1/GSTR-1A and is non-editable (GSTN advisory, June 2025). There is no notified rule that locks the ITC figures in Table 4, and no "Zero Mismatch" rule has been notified.
2. Invoice Management System (IMS)
IMS has been available since October 2024 and is optional. You can accept, reject or keep invoices pending; invoices with no action are deemed accepted. From the October 2025 period, credit notes can be kept pending for only one tax period.
3. DRC-01C Intimations
If ITC claimed in GSTR-3B exceeds ITC in GSTR-2B by more than the limit set on the portal, a DRC-01C intimation is generated (Rule 88D). Reply within 7 days by reversing the excess through DRC-03 or explaining it in Part B.
How to Fix ITC Mismatch
Step 1: Download GSTR-2B
Download GSTR-2B for relevant period from GST portal.
Step 2: Match Invoice by Invoice
Compare each invoice in purchase register with GSTR-2B:
- Invoices present in both
- Invoices only in books
- Invoices only in GSTR-2B
Step 3: Follow Up with Suppliers
For invoices missing in GSTR-2B:
- Contact supplier to confirm GSTR-1 filing
- Request GSTR-1 filing or amendment
- If they fail, consider reversing ITC
Step 4: Use IMS for Reconciliation
Use the Invoice Management System (IMS) to accept, reject, or keep invoices pending before filing GSTR-3B. It allows:
- Weekly IMS reconciliation
- Strategic use of Pending status where goods yet to be received
- Recompute GSTR-2B function after changes
Step 5: Respond to DRC-01C Notices
If you receive a DRC-01C intimation, reconcile the difference and, within 7 days, either reverse the excess ITC through DRC-03 or explain it in Part B of DRC-01C.
4. Books vs GSTR-2B: ITC Recording Mismatch
The Problem: ITC recorded in books does not match ITC available in GSTR-2B.
Common Causes
| Cause | Description |
|---|---|
| Invoice Not in GSTR-2B | Supplier has not filed GSTR-1 |
| Supplier Non-Compliance | Supplier failed to pay tax or file returns |
| Invoice Not in Books | Purchase invoice in GSTR-2B but not in books |
| Supplier Amendments | Supplier amends an invoice in a later GSTR-1, so the change shows in a later GSTR-2B |
| Ineligible ITC Claimed | ITC claimed on blocked credits (motor vehicles, food, etc.) |
How to Fix
- Reconcile ITC claimed in GSTR-3B with books and GSTR-2B
- Identify and reverse ineligible ITC
- Follow up with suppliers for missing invoices
- Monitor GSTR-2B amendments proactively
- Check IMS action status (accepted, rejected, pending) before GSTR-3B
5. E-invoice vs GSTR-1: IRN Mismatch
The Problem: E-invoices generated (with IRN) do not match GSTR-1 B2B supplies.
Common Causes
| Cause | Description |
|---|---|
| IRN Gap | E-invoice generated but not in GSTR-1 |
| Timing Difference | IRN generated in one period, GSTR-1 in another |
| Invoice Amendment | Amended invoice causing mismatch with original IRN |
| Cancellation Issues | E-invoice cancelled but not reflected in GSTR-1 |
How to Fix
- Generate e-invoice first before filing GSTR-1
- Reconcile IRN list with GSTR-1 B2B supplies
- Check timing differences. IRN may be in next period
- If amendment unavoidable, maintain reconciliation statement explaining mismatch
What Happens If You Ignore It
Where e-invoicing applies, IRP data auto-populates GSTR-1 B2B tables. Gap between IRN data and GSTR-1 stands out immediately to department.
6. E-way Bill vs GSTR-1: Movement vs Supply Mismatch
The Problem: E-way bills generated do not match GSTR-1 outward supplies.
E-way bills track movement of goods, while GSTR-1 tracks supplies. They rarely match exactly. Learn how to generate and manage e-way bills step-by-step to prevent hidden mismatches.
Common Causes
| Cause | Description |
|---|---|
| Unreported Supply | E-way bill generated but no supply in GSTR-1 |
| GSTIN Identity Theft | E-way bill generated against your GSTIN without knowledge |
| Timing Difference | E-way bill in one period, GSTR-1 in another |
| Stock Transfer | Stock transfers require e-way bills but not "supplies" |
| Job Work | Job work movements require e-way bills but not "supplies" |
How to Fix
- Compare e-way bill outward supplies with GSTR-1 invoices
- Detect unreported sales or wrong GSTIN / value mismatch
- For stock transfers and job work, document movement type
- For GSTIN identity theft, report immediately to department
What Happens If You Ignore It
A goods invoice in GSTR-1 that needed an e-way bill but has none, or an e-way bill with no matching supply, is easy for the department to spot in data analytics, and reconciliation turns into notice handling.
7. E-way Bill vs E-invoice: Internal Consistency Check
The Problem: E-way bills and e-invoices do not match.
Common Causes
| Cause | Description |
|---|---|
| E-invoice Generated First | E-invoice generated, e-way bill missing |
| E-way Bill Generated First | E-way bill generated, e-invoice missing |
| Value Mismatch | Values in e-invoice and e-way bill differ |
| GSTIN Mismatch | Different GSTINs in e-invoice and e-way bill |
How to Fix
- Generate e-invoice first when e-invoicing applies
- Generate e-way bill based on e-invoice
- Ensure consistency in values, GSTINs, and HSN codes
- If cancellation not possible, maintain reconciliation statement for audits
Reconciliation Checklist
Monthly Reconciliation
- Books → GSTR-1: All sales in books reported in GSTR-1
- GSTR-1 → GSTR-3B: Liability in GSTR-3B matches GSTR-1
- GSTR-2B → GSTR-3B: ITC claimed in GSTR-3B matches GSTR-2B
- Books → GSTR-2B: ITC in books matches GSTR-2B
- E-invoice → GSTR-1: IRN data matches GSTR-1 B2B supplies
- E-way bill → GSTR-1: E-way bills match GSTR-1 outward supplies
- IMS review (accept, reject or keep pending before GSTR-3B)
Quarterly Reconciliation
- HSN Summary (GSTR-1 Table 12) reconciliation with sales register
- Turnover reconciliation between GST and Income Tax
- ITC reconciliation across all GSTINs (if multiple)
Annual Reconciliation
- GSTR-9 vs Books
- GSTR-9 vs GSTR-1, GSTR-3B, GSTR-2B
- GSTR-9C self-certified reconciliation statement (AATO above Rs 5 crore)
What Happens If You Don't Reconcile?
| Scenario | Consequence |
|---|---|
| GSTR-1 vs GSTR-3B mismatch | ASMT-10 scrutiny notice, DRC-01B notice |
| ITC mismatch (GSTR-3B > GSTR-2B) | DRC-01C system-generated intimation |
| E-invoice mismatch | Scrutiny notice, ITC denial |
| E-way bill mismatch | Scrutiny notice, potential penalty |
| Ignoring notices | Confirmed tax demands, interest, penalties |
How Tax Garden Helps
GST return reconciliation is critical compliance function requiring systematic effort and attention to detail. Single unreconciled mismatch can trigger notices, ITC reversals, and tax demands.
Through our GST return filing service, Tax Garden's GST experts help you:
- Reconcile Books vs GSTR-1 vs GSTR-3B vs GSTR-2B
- Identify and fix GSTR-1 and GSTR-3B mismatches
- Manage ITC reconciliation and IMS compliance
- Reconcile e-invoice and e-way bill data with GSTR-1
- Respond to GST mismatch notices (ASMT-10, DRC-01B, DRC-01C)
Sources: GST portal (gst.gov.in); Tally Solutions; TaxGuru; ClearTax; TaxOne; TechTax; IndiaFilings; Kanakkupillai; TaxRobo; Ledgers Cloud; Shriram Finance. Verify current rules, due dates, and procedures on gst.gov.in before acting. This article is general information on GST return reconciliation and not substitute for professional advice.
