Regular Dealer Monthly GST Checklist for 2026

Monthly GST Due Date Snapshot

These are the general due dates. The government may extend them for a particular period, state, or category of taxpayer.

Quarterly Return Monthly Payment (QRMP) Due Dates

A QRMP taxpayer may use the optional Invoice Furnishing Facility during the first two months of a quarter. IFF is generally available up to the 13th of the following month, while tax is generally deposited through Form GST PMT-06 by the 25th.

Quarterly GSTR-3B is generally due on the 22nd or 24th after the quarter, depending on the applicable state group.

Step 1: Close the Books

Record All Monthly Transactions

Record all sales and purchase invoices, credit and debit notes, returns, branch transfers, taxable advances, exports, SEZ supplies, reverse-charge transactions and cancelled documents up to the last day of the month.

A missed purchase invoice may delay ITC, while an omitted sales invoice may understate tax liability.

Reconcile E-Invoices and E-Way Bills

Where e-invoicing applies, compare the sales register with Invoice Registration Portal data. Investigate invoices without an Invoice Reference Number (IRN), IRNs missing from the books, cancelled IRNs recorded as active, missing credit or debit notes, and differences in value, tax rate or place of supply .

Under Notification No. 10/2023-Central Tax , e-invoicing generally applies where aggregate annual turnover exceeded ₹5 crore in any preceding financial year from FY 2017-18 onwards, subject to the notified exemptions. This threshold has applied from 1 August 2023.

From 1 April 2025, taxpayers with aggregate annual turnover of ₹10 crore or more must report prescribed invoices, credit notes and debit notes to the IRP within 30 days of the document date.

Also match invoices and delivery challans with e-way bills. Check for unmatched records, cancelled invoices, incorrect GSTINs and goods moved without the required document. The portal restricts e-way bill generation against a base document older than 180 days and total extension beyond 360 days from the original generation date.

Current Update: The proposed mandatory Ship-to GSTIN and voluntary e-way bill closure changes were put on hold on 29 July 2026. Do not treat them as mandatory until GSTN announces a new date.

Review Tax Treatment

Check the GST rate, HSN or SAC, cess, exemption conditions, place of supply and B2B or B2C classification, particularly for new items and supplies billed after a long gap.

A wrong place of supply can result in CGST and SGST being charged instead of IGST, or the reverse. This may require fresh tax payment and a separate refund claim.

Identify Reverse-Charge Transactions

A purchase from an unregistered supplier does not automatically attract reverse charge. Review the expense and purchase ledgers only for supplies covered by the Act or an applicable notification. For each applicable transaction:

1. Determine the time of supply.
2. Check whether a self-invoice or payment voucher is required.
3. Apply the correct rate and tax head.
4. Pay the liability through the electronic cash ledger.
5. Claim ITC only after payment and after confirming eligibility.

Note: RCM tax cannot be paid using input tax credit.

Step 2: Prepare and File GSTR-1

Match GSTR-1 With the Sales Register

The main comparison should be between the books and GSTR-1 . Comparing only GSTR-1 with GSTR-3B may not reveal an error because outward liability is auto-populated.

Validate GSTINs and Return Details

Validate customer GSTINs and review HSN reporting, document series, cancelled numbers, amendments and credit notes.

Pay particular attention to new customers, suspended or cancelled registrations, multiple-GSTIN businesses and bill-to or ship-to transactions. An incorrect GSTIN may prevent the invoice from reaching the intended recipient’s IMS.

Report Credit Notes on Time

A GST credit note relating to a financial year must be declared by the earlier of:

• 30 November following the end of that financial year, or
• The date of filing the relevant annual return

A commercial credit note may still be issued later, but it may not reduce GST liability under Section 34 after this time limit.

Correct Errors Through GSTR-1A

GSTR-1A can be used after filing GSTR-1 and before filing GSTR-3B for the same period. From the July 2025 tax period, outward liability auto-populated from GSTR-1, GSTR-1A, or IFF is non-editable in GSTR-3B. Correct any missed or incorrect outward-supply details through GSTR-1A before filing GSTR-3B.

Step 3: Review IMS and Input Tax Credit

Take the Correct IMS Action

A supplier document appearing in IMS may be accepted, rejected, kept pending, or left without action, depending on the document type and current portal rules.

A record with no action may be treated as deemed accepted for GSTR-2B generation. This does not make blocked, personal, or otherwise ineligible ITC claimable.

Reject a document only where it does not belong to the business or needs supplier correction. Use the pending option only where it is available, and the transaction is genuinely unresolved.

Reconcile GSTR-2B With the Purchase Register

Draft GSTR-2B is generally generated on the 14th. Group differences by the action required.

If an IMS action changes after draft GSTR-2B is generated, recompute GSTR-2B before finalising the ITC claim.

GSTN introduced an Excel-based IMS Offline Tool in April 2026 for individual and bulk actions. It can support reconciliation but does not determine legal ITC eligibility.

Check ITC Eligibility

Under Section 16(4), ITC must generally be claimed by the earlier of 30 November following the relevant financial year or the date of filing the annual return.

Imports, ISD credit and reverse-charge ITC should be reviewed separately because they do not all follow the normal supplier-invoice flow.

Check the 180-Day Payment Rule

Where Rule 37 applies, ITC must be reversed in proportion to the invoice value and tax not paid to the supplier within 180 days, together with applicable interest. The credit may be reclaimed after payment. This 180-day condition does not apply to supplies on which tax is payable under reverse charge.

For example, if ITC of ₹18,000 was claimed and 40% remains unpaid, the starting reversal calculation would be ₹7,200. Maintain an exception register showing the supplier, amount, reason, action owner, and expected resolution date.

Step 4: Prepare GSTR-3B and Pay Tax

Verify Liability and ITC

Compare the final GSTR-1 and GSTR-1A figures with the sales and output-tax ledgers. Reconcile Table 4 of GSTR-3B with the final GSTR-2B and the ITC working prepared earlier. Confirm that reversals, reclaims, imports, ISD credit and RCM credit have been treated correctly. Do not claim an amount only because it is auto-populated.

Review Interest and Earlier-Period Liability

Review liabilities relating to earlier periods, the period to which each liability belongs, the interest shown in Table 5.1 and your own calculation.

GSTN issued an advisory on 16 April 2026 for recomputation of interest under Table 5.1. Use the portal facility where applicable, but keep an independent calculation.

Check the Electronic Ledgers

Confirm that challan payments are reflected before filing.

Apply the ITC Utilisation Order

UTGST credit cannot be used against CGST liability. RCM liability, interest, penalty and late fee must be paid through the electronic cash ledger.

Check Rule 86B

Where monthly taxable supplies, excluding exempt and zero-rated supplies, exceed ₹50 lakh, check whether Rule 86B restricts the use of the electronic credit ledger.

The rule generally limits credit-ledger payment to 99% of output tax liability unless an exception applies. Keep the monthly calculation and evidence supporting any exception claimed.

Step 5: Complete Post-Filing Checks

Save the Monthly GST Records

Section 36 generally requires GST records to be retained for 72 months from the due date of the annual return. Records connected with an appeal, investigation or proceeding may need to be kept longer.

Track Unresolved Items

Maintain one tracker for pending IMS documents, missing supplier invoices, disputed credit notes, Rule 37 reclaims, return amendments, unmatched e-invoices and tax deposited under the wrong head. Each item should have an owner and expected closure date.

Review Old Pending Returns

The three-year filing restriction under Sections 37, 39, 44 and 52 was brought into force from 1 October 2023 through Notification No. 28/2023-Central Tax.

GSTN implemented the restriction on the portal from the November 2025 tax period. Under its October 2025 advisory, the first illustrated set of affected returns was blocked from 1 December 2025.

Who Handles Each Task?

The accountant or finance team should manage return preparation, IMS actions, ITC review, RCM, tax set-off, filing and record retention.

Business owners and branch teams should ensure that transactions reach accounts on time, customer and supplier GSTINs are correct, goods move with the required documents and supplier or branch differences are resolved before filing.

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Keep invoices, GST reports and reconciliation records connected through one accounting workflow. BUSY accounting software can help your team organise GST data and review return differences before filing.

Conclusion

A reliable monthly process under the GST regular scheme begins with complete books. Reconcile outward supplies before GSTR-1, review ITC before GSTR-3B, and retain supporting records after filing. Closing differences every month creates a stronger audit trail and reduces the risk of avoidable notices.