GST filing entails more than just turning in GSTR-1 and GSTR-3B forms on time. A return may be filed on time but yet contain errors that result in extra tax payment, improper Input Tax Credit (ITC), customer complaints, or notices later. In 2026, taxpayers will also need to pay closer attention to GSTR-2B, the Invoice Management System (IMS), GSTR-1A, and GST record reconciliation.
The GST Portal now permits qualified GSTR-1 errors or omissions to be corrected using GSTR-1A before filing GSTR-3B for the same tax period. Sharda Associates assists businesses in reviewing GST returns, reconciling sales and ITC, identifying filing problems, and managing GST compliance before minor mistakes become major concerns.
1. Filing GSTR-1 Without Reconciling Sales
One of the most common blunders is uploading GSTR-1 directly from accounting data without first verifying that it matches the real sales records.
Before filing, businesses should verify their GST sales register against invoices, credit notes, debit notes, and other relevant accounting records.
An inaccurate GSTIN, invoice number, taxable value, or tax amount might impair both the supplier’s return and the recipient’s ITC records.
GSTR-1 is the statement used to provide outward-supply facts on the GST Portal; hence, accuracy at this stage is critical.
2. Showing Different Turnover in GSTR-1 and GSTR-3B
GSTR-1 and GSTR-3B have different functions, but the outward-supply and tax-liability statistics must be reconciled correctly.
GSTR-3B is the summary return in which the taxpayer declares GST liabilities and other relevant information for the tax period.
Suppose the taxable external supply recorded in GSTR-1 is ₹20 lakh, but the corresponding liability in GSTR-3B is calculated on ₹18 lakh without a good explanation.
That discrepancy should be recognized before filing, rather than being discovered after annual reconciliation.
Not every difference indicates that taxes have been dodged, but unexplained disparities might cause unneeded compliance issues.
3. Claiming ITC Without Checking GSTR-2B
Claiming ITC solely because a purchase invoice is included in the accounting software is problematic.
GSTR-2B is an auto-drafted ITC statement prepared using information provided by suppliers and other relevant sources.
Before filing GSTR-3B, firms should reconcile their purchase register with GSTR-2B to discover missing or duplicate invoices, invalid GSTINs, and credit notes.
If a significant purchase invoice is missing, the first step should usually be to determine why it is missing rather than simply claiming credit.
4. Ignoring the Invoice Management System
IMS has emphasized the importance of reviewing purchasing invoices.
Depending on the transaction and system treatment, the recipient can accept, reject, or leave eligible records pending. According to the GST Portal’s IMS guidance, rejected records do not auto-populate as ITC in GSTR-3B, while pending records remain outside the relevant GSTR-2B/GSTR-3B computation until addressed appropriately.
As a result, businesses should avoid treating IMS as an optional screen that no one needs to review.
For example, accidentally rejecting a genuine supplier invoice can have an impact on ITC. Similarly, accepting an improper invoice without verifying the GSTIN, value, and supply details might lead to reconciliation issues.
5. Claiming Ineligible ITC
Not all GST paid on company purchases is immediately available as ITC.
The GST law includes prerequisites for ITC, as well as particular restrictions and blocked-credit rules. Documentary standards must also be met.
Businesses frequently make mistakes when purchasing items for personal use, certain motor vehicles, food and beverages, club-related expenses, construction-related expenses, or goods that are lost, stolen, destroyed, written off, or given away as gifts or free samples, subject to statutory exceptions.
The ideal method is to investigate the nature and purpose of the expense, rather than just claiming every GST amount displayed in the purchase ledger.
6. Selecting IGST Instead of CGST and SGST—or Vice Versa
An incorrect determination of the place of supply can result in the wrong sort of tax being imposed.
A transaction that should be subject to IGST may be improperly displayed as CGST and SGST, or an intra-State transaction may be classified as inter-State.
This error is especially common when the billing address, location of supply, and real nature of the transaction are not thoroughly examined.
Fixing the tax head after the return is submitted can be significantly more inconvenient than examining the invoice before filing.
Businesses that interact with customers from different states should have a clear invoice-review process rather than relying on automation to make every GST decision automatically.
7. Entering Credit Notes and Debit Notes Incorrectly
Credit and debit notes have a substantial impact on GST liability.
In proper conditions, a credit note reduces the value or tax due, while a debit note raises it.
Confusing the two can have the exact opposite tax impact that the firm anticipated.
Businesses should double-check the note type, original invoice reference, taxable value, and GST impact before inserting the document in GSTR-1.
If an omission or error in outward-supply reporting is detected after filing GSTR-1 but before GSTR-3B for the same tax period, taxpayers should determine if it can be repaired through GSTR-1A. According to the GST Portal, GSTR-1A can be submitted after GSTR-1 but before GSTR-3B for the same period is filed.
8. Forgetting Reverse Charge Liability
Businesses may focus solely on GST levied by suppliers, ignoring transactions in which tax may be payable by the recipient via the Reverse Charge Mechanism (RCM).
This raises two potential issues: the tax liability itself may be omitted, and the associated ITC treatment may be handled wrongly.
A monthly GST review should therefore include a separate check for transactions that may be subject to reverse charge, rather than relying solely on the sales and purchase records.
Legal expenses, defined transport transactions, and other notified categories may necessitate special care, depending on the circumstances of the transaction.
9. Filing Late—or Filing on Time Without Paying Attention to Tax Payment
A return submitted beyond the required time may incur late fees, while a delayed tax payment may result in interest under the GST regime.
Taxpayers should also be aware that GST filing deadlines vary depending on the return and taxpayer profile.
For example, under the QRMP Scheme, eligible taxpayers file GSTR-1 and GSTR-3B quarterly while paying taxes monthly.
As a result, a company should create its own compliance calendar rather than presuming that all GST taxpayers follow the same monthly filing schedule.
When the government formally extends a due date, the extended date must be followed. Businesses should not expect an extension just because a portal issue or general press item has surfaced.
10. Filing the Return Without a Final Reconciliation
Perhaps the biggest avoidable error is treating the GST return as complete as soon as the statistics are entered into the system.
Before submitting, businesses should compare their sales, credit/debit notes, tax liability, purchase records, GSTR-2B, IMS activities, and electronic ledgers.
The GST Portal now includes a variety of data points to assist businesses in identifying discrepancies before they become year-end concerns. GSTR-2B generates an auto-drafted ITC view, IMS influences the treatment of supplier records, and GSTR-1A allows eligible revisions to outward-supply information prior to GSTR-3B submission.
The most effective GST approach is not to file first and then reconcile. It’s reconcile first, then file.
What Should You Check Before Clicking “File”?
A practical GST filing review does not have to be complex.
Enquire whether sales in the books are consistent with outward-supply reporting, whether credit and debit notes have been appropriately classified, whether GSTR-2B has been reconciled, whether IMS actions have been evaluated, and whether any reverse-charge liability is outstanding.
Then, compare the final tax liability to the computerized ledgers, making sure that the individual completing the return understands any significant differences from the prior month.
This little review can save numerous corrections later.
Conclusion
Most GST filing problems do not begin with complicated tax disputes. They begin with small errors—a wrong GSTIN, an unreported credit note, an ITC mismatch, an incorrect tax head, or a return filed without proper reconciliation.
In 2026, taxpayers have more digital information available through GSTR-2B, IMS, and GSTR-1A, but these tools are useful only when someone actually reviews them before filing.
The safest approach is to make GST reconciliation part of the monthly or quarterly accounting process rather than waiting until the annual return or a notice identifies the problem.
Sharda Associateshelps businesses review GST data, correct mismatches, manage ITC, and prepare returns using the actual books and supporting documents so that GST filing is based on reconciled information rather than last-minute figures.
Frequently Asked Questions
Q1: What are the most typical GST filing mistakes?
Common GST filing errors include improper sales reporting, inconsistencies between GSTR-1 and GSTR-3B, claiming incorrect ITC, neglecting GSTR-2B or IMS, incorrect tax categorization, and missing reverse charge liability.
Q2: Why should GSTR-1 be reconciled before filing?
GSTR-1 should be reconciled with the sales register, invoices, credit notes, debit notes, taxable values, and GST amounts to avoid reporting errors and any reconciliation concerns.
Q3. What happens if GSTR-1 and GSTR-3B have different turnovers?
A discrepancy between GSTR-1 and GSTR-3B may necessitate reconciliation and explanation. Unexplained variances can raise compliance problems and necessitate correction or additional clarification.
Q4. Why is GSTR-2B necessary for collecting ITC?
GSTR-2B generates an automatically constructed perspective of applicable ITC based on supplier-reported data. Businesses should reconcile it with their purchase records before claiming ITC on GSTR-3B.
Q5. What is the Invoice Management System (IMS) in GST?
The Invoice Management System enables recipients to analyze supplier-reported invoice records and take appropriate actions, such as accepting, rejecting, or leaving eligible records pending.
Q6. Can I claim ITC for all company purchases?
No, the GST law includes eligibility limitations, documentation requirements, and mechanisms for blocked credits. Businesses should confirm the nature and purpose of each spending before claiming ITC.
Q7: What is the difference between IGST and CGST/SGST?
IGST applies to qualifying interstate supplies, while CGST and SGST apply to intrastate goods. The relevant tax treatment is determined by the applicable place-of-supply laws.
Q8: How should credit and debit notes be stated on GST returns?
Credit and debit notes should be documented precisely, including the necessary invoice reference, taxable value, tax amount, and GST treatment, as they might have a direct impact on tax liabilities.
Q9: What is GSTR-1A, and when can it be used?
GSTR-1A allows eligible taxpayers to change or add certain outward-supply details after submitting GSTR-1 but before filing GSTR-3B for the same tax period.