Many businesses and even some practitioners still use “2A” and “2B” interchangeably. This is not just imprecise — it can damage your legal position in an audit. The two statements are fundamentally different.

Here is the practical consequence: if your supplier filed GSTR-1 on the 13th of a month, that invoice appears in your GSTR-2A on the 13th. But if the GSTR-2B for that month was already generated on the 14th of the previous month, that invoice will appear only in next month’s GSTR-2B. GSTR-2A shows it; GSTR-2B does not — yet. Claiming it in the current month’s GSTR-3B creates a mismatch. You wait for next month’s GSTR-2B before claiming.

Effective from January 1, 2022, Section 16(2)(aa) of the CGST Act made GSTR-2B matching a legal condition for ITC eligibility. The provision states that ITC is available only in respect of invoices or debit notes that have been furnished by the supplier in their statement of outward supplies (GSTR-1) and communicated to the recipient — meaning, appear in GSTR-2B.

Possession of a valid tax invoice is necessary but no longer sufficient. Even if you have the physical invoice, paid the supplier, received the goods, and the supplier paid the GST — if they have not filed GSTR-1 and the invoice is not in your GSTR-2B, you cannot claim ITC in that month. This is the strict legal position as of 2026.

The practical consequence: ITC eligibility is now partly in your supplier’s hands. A non-filing supplier does not just hurt themselves — they hurt every customer whose ITC is blocked until the filing happens.

Not all mismatches are the same, and the action required differs significantly by category. I find it useful to think of them in five buckets:

Category 1 — Timing Difference (Most Common)

Your supplier filed GSTR-1 after the GSTR-2B generation date for the month. The invoice exists, the GST was paid, the filing happened — just too late for this month’s GSTR-2B. The credit will appear in next month’s GSTR-2B.

Action: Wait for next month’s GSTR-2B. Do not claim in the current month. Mark these invoices in your reconciliation register as “pending — next month.” No reversal needed, no interest, no risk — just timing.

Category 2 — Supplier Has Not Filed At All

The supplier has not filed their GSTR-1 — not just late, but completely absent. You have paid them, including the GST. But the tax does not reflect anywhere in the system as far as your ITC is concerned.

Action: Contact the supplier in writing immediately. Use the GST portal’s “Communication with Taxpayer” facility to create an auditable record of the follow-up. If the supplier continues to be non-compliant and the Section 16(4) deadline is approaching, you face a real risk of permanent ITC loss. Consider withholding future payments until their GST compliance is current — this is the most effective commercial lever available.

Category 3 — Error in Supplier’s GSTR-1

The supplier filed their GSTR-1, but with an incorrect GSTIN, wrong invoice amount, or wrong period. The invoice exists in the system but does not match your records — or appears in the wrong company’s GSTR-2B entirely.

Action: The supplier needs to amend their GSTR-1 (using GSTR-1A or the amendment process). Only the supplier can fix their own GSTR-1. Communicate the specific error clearly and document the request. Until the correction reflects in your GSTR-2B, the ITC cannot be claimed.

Category 4 — ITC Already Claimed (Excess Claim)

You claimed ITC in GSTR-3B that does not appear in GSTR-2B — meaning you claimed more than you were entitled to. This is the category that generates DRC-01C notices and attracts interest at 18% per annum from the date of filing.

Action: Voluntary reversal via DRC-03 — with interest at 18% for the period the excess credit was used. Do not wait for a notice. Self-reversal before notice is treated more favourably than post-notice reversal.

Category 5 — Credit Notes and Adjustments

A supplier has issued a credit note reversing part of an earlier invoice. This reduces your available ITC. If the credit note appears in your GSTR-2B but you have not reversed the corresponding ITC in GSTR-3B, you have an excess claim.

Action: Reverse the ITC corresponding to the credit note in the next GSTR-3B. Maintain a credit note register that tracks these separately from invoice-level ITC.

Before IMS, the reconciliation process was largely manual — download GSTR-2B, download your purchase register from your accounting software, compare the two in Excel, identify gaps, and make decisions. From April 1, 2026, this process has a statutory overlay.

Under the IMS framework, invoices filed by your supplier appear on the IMS dashboard. You can take one of three actions on each invoice: Accept (ITC flows to GSTR-2B), Reject (ITC does not flow, supplier is notified), or Pending (no action yet). If you take no action within the prescribed window, the invoice is deemed accepted.

The critical point is that the IMS is not just a convenience tool — it is now the statutory basis for GSTR-2B generation. The section 38 substitution by Notification 16/2025-CT makes ITC legally tied to IMS acceptance records. This has two implications:

• If you reject an invoice in IMS (perhaps because you received a defective supply), the ITC does not flow to GSTR-2B for that invoice — even if the supplier has paid the GST
• The deemed acceptance provision means businesses that do not actively monitor IMS may inadvertently accept invoices they should have rejected — creating ITC claims that are later challenged

This is the provision that causes the most financial pain when missed. Section 16(4) sets a hard deadline for claiming ITC for a given financial year. Once that deadline passes, the credit is gone — no rectification, no revision, no appeal remedy for the lapse itself.

The Deadline: Earlier of Two Dates

• The due date of the GSTR-3B for the month of November following the end of the financial year — for FY 2025-26, this means the November 2026 GSTR-3B (due December 20, 2026)
• The date of filing the Annual Return (GSTR-9) for that financial year — whichever comes first

Internal Deadline: Aim for September

The legal deadline is November. But a practical internal deadline of September is much safer. September gives you September and October to chase suppliers who have not filed, correct errors that appear in GSTR-2B, and handle any late-appearing invoices before the window closes in November. Businesses that target September for FY ITC completion almost never miss the November deadline. Businesses that start in October frequently do.

When the GSTN system detects a significant mismatch between ITC claimed in your GSTR-3B and ITC appearing in your GSTR-2B, it generates a DRC-01C intimation automatically. The notice lists the mismatch amount and asks for one of three responses:

1. Confirm that the ITC difference represents excess claim and pay the differential tax with interest via DRC-03
2. Provide an explanation for the difference — that it is a timing issue, supplier error, or other eligible reason
3. A combination — partially accept the excess and explain the remainder

The response deadline is typically 15 to 30 days from the notice date. A non-response is treated as acceptance of the demand — which then becomes payable with interest and potentially penalty. Do not ignore DRC-01C.

How to Prepare Your Response

Start by categorising every rupee of the mismatch into the five buckets described earlier. Timing differences with evidence (supplier filed late, GSTR-2B for the next month shows the credit) are fully defensible. Supplier non-filing with documented follow-up attempts is also defensible to an extent. Excess claims that cannot be explained need to be accepted and reversed with DRC-03.

Attach: your purchase register extract for the relevant period, GSTR-2B downloads showing what was and was not available, evidence of supplier follow-up communications, and a reconciliation statement mapping each invoice to its treatment.

Going back to the manufacturer I mentioned at the start. His ₹4.3 lakh mismatch broke down as follows once we categorised it:

The notice was substantially resolved. The financial cost was the interest on the excess claim (around ₹8,000) — not ₹4.3 lakh. The difference between a catastrophic outcome and a manageable one was entirely in the quality of the reconciliation and the documentation of supplier follow-ups.

1. After the 14th — Download GSTR-2B for the month from the GST portal. This is your authoritative ITC document for the month.
2. Export your Purchase Register from Tally/accounting software for the same period — showing all purchase invoices and their GST amounts.
3. Match line by line — supplier GSTIN, invoice number, invoice date, taxable value, GST amount. Flag every line that does not match perfectly.
4. Categorise mismatches into the five buckets. For each category, determine the required action and who is responsible — your team or the supplier.
5. Send supplier follow-ups for Category 2 and Category 3 immediately — in writing, with the specific invoice details that need correction or filing.
6. File GSTR-3B by the 20th claiming only the ITC that appears in GSTR-2B. Do not claim ITC that is not yet in GSTR-2B — even if you are confident it will appear next month.
7. Carry forward a tracker of all “pending” invoices — expected month, supplier name, amount, follow-up status. This tracker is your ITC pipeline and needs active management month to month.

Total time for a business with 50-100 purchase invoices per month: about two to three hours on the 15th or 16th. For businesses with higher volumes, dedicated software that pulls both GSTR-2B and purchase register data automatically reduces this to verification rather than manual matching.

Using GSTR-2A instead of GSTR-2B as the ITC basis:
Since January 2022, Section 16(2)(aa) references GSTR-2B — not GSTR-2A. Claiming ITC based on GSTR-2A (which is dynamic and may show invoices not yet in GSTR-2B) creates mismatches. Always claim only what is in GSTR-2B for that month.

Filing GSTR-9 before completing ITC reconciliation:
Once GSTR-9 is filed, the Section 16(4) window closes for that FY. Any ITC not yet claimed is permanently lost. Complete all reconciliation and claim outstanding ITC in GSTR-3B before touching the GSTR-9 filing button. This sequencing error can cost lakhs — and has, for clients I have had to deliver bad news to.

Not documenting supplier follow-ups:
When a DRC-01C arrives and the explanation is “supplier filed late,” the department wants evidence of good-faith follow-up. A WhatsApp message is better than nothing. A written email is better. A communication via the GST portal’s taxpayer communication facility is best — it creates a timestamped, government-portal record that is very difficult to dispute. Use it.

Ignoring small mismatches every month and doing an annual cleanup:
Small mismatches compound. Twelve months of ₹15,000 timing differences from the same vendor become ₹1.8 lakh of unresolved mismatch by year-end — some of which may be approaching the Section 16(4) deadline. Monthly cleanup is significantly less painful than an annual one done under time pressure.
GST Compliance for MSMEs — Complete Guide