Standard Operating Procedure: GST Internal Audit

This Standard Operating Procedure (SOP) provides a comprehensive framework for conducting an internal GST audit. The objective is to verify the accuracy of GST filings, ensure compliance with statutory provisions, identify potential tax leakages, and mitigate risks of litigation or penalties. This audit should be performed periodically (quarterly or half-yearly) to ensure that the organization’s financial records align seamlessly with the GST portal data.

1. Pre-Audit Preparation and Data Collation

• Collect all monthly GSTR-1, GSTR-3B, and GSTR-2B returns for the period under audit.
• Extract the General Ledger (GL) from the accounting software for Output Tax, Input Tax, and GST Expense accounts.
• Verify the reconciliation between the Sales Register and GSTR-1.
• Verify the reconciliation between the Purchase Register and GSTR-2B.
• Ensure that the trial balance matches the tax liability accounts.

2. Review of Output Tax Liability

• Sales Reconciliation: Compare the total revenue reported in the books of accounts with the total taxable value reported in GSTR-1.
• Classification Audit: Verify that the HSN/SAC codes used match the nature of goods/services supplied.
• Tax Rate Verification: Check if the correct GST rates (5%, 12%, 18%, 28%) have been applied to specific products or service categories.
• Exempt/Zero-rated Supplies: Audit export invoices (with/without payment of IGST) and ensure proper documentation like shipping bills and LUTs are in place.
• Time of Supply: Ensure that GST liability is recognized at the earliest of invoice issuance or receipt of payment.

3. Review of Input Tax Credit (ITC)

• Eligibility Check: Verify that all claimed ITC pertains to business-related expenses and is not restricted under Section 17(5) of the GST Act (e.g., personal consumption, motor vehicles, construction material).
• Vendor Compliance: Confirm that ITC is claimed only for invoices appearing in GSTR-2B and where the vendor has filed their GSTR-1.
• Payment Condition: Ensure the 180-day rule is met—tax must be paid to the vendor within 180 days; otherwise, ITC must be reversed.
• Reversal Audit: Verify that proportional reversals are made for common credits used for both taxable and exempt supplies.

4. Documentation and Filing Accuracy

• Invoice Consistency: Sample check invoices for mandatory fields: GSTIN of supplier/recipient, HSN code, Place of Supply, and tax breakdown.
• Credit/Debit Notes: Verify that credit notes are issued within the statutory time limits and reflected correctly in filings.
• RCM Compliance: Identify expenses subject to Reverse Charge Mechanism (RCM) and ensure the tax was self-assessed and paid via GSTR-3B.
• E-Way Bill Compliance: Cross-verify E-Way bills generated against sales invoices to ensure timing and value consistency.

5. Pro Tips & Pitfalls

• Pro Tip: Automate the GSTR-2B to Purchase Register reconciliation process using GST compliance software to save time and increase accuracy.
• Pro Tip: Always document the "audit trail." If you identify an error, keep a record of the correction mechanism used to justify your stance during an official departmental audit.
• Pitfall - The "Payment" Gap: Many companies claim ITC based on the invoice date but forget to verify if the vendor has filed their return. Relying solely on your own records without checking GSTR-2B is the #1 cause of tax notices.
• Pitfall - Misclassification: Incorrectly classifying a service as a "good" or choosing the wrong GST rate is a common trigger for Departmental audits. Review your master data periodically.

FAQ

Q: What should we do if we find an ITC claim for which the vendor has not paid the tax? A: Immediately reverse the ITC in your GSTR-3B for the current month. You can re-claim this ITC once the vendor files their return and the transaction appears in your GSTR-2B.

Q: Is it mandatory to perform a reconciliation every month? A: While the law requires periodic compliance, it is highly recommended to perform a monthly reconciliation between GSTR-2B and your Purchase Register to avoid interest penalties and discrepancies at the end of the financial year.

Q: How long should we retain GST-related documents? A: As per the GST law, all accounts and records must be maintained for a period of at least 72 months (6 years) from the due date of furnishing the annual return for the relevant financial year.

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