Last reviewed: 25 September 2026. Wrongly claimed input tax credit is one of the most expensive GST errors a business makes – it comes back with interest, and now with the auto-population regime, a mismatch surfaces on the portal before you even finish filing. Since we first published this checklist, the government has locked outward liability, made ITC a GSTR-2B/IMS-driven auto-populated figure, and is expected to remove manual override of Table 4A altogether. This update walks through all nine checks, what has actually changed on the portal versus what is still only proposed, and two worked examples so the reversal arithmetic is never a guess.
At a glance
What has actually changed on the GST portal
Reconciliation discipline has shifted from "adjust at filing time" to "verify through the month", in three phases. Two are live; the third is announced but, as of this review, not confirmed by a dated GSTN advisory – a distinction worth getting right before you tell a client something is mandatory.
| Phase | Status | What it means for you |
|---|---|---|
| Outward liability (Table 3.1/3.2) locked, sourced from GSTR-1/1A/IFF | Live since July 2025 (GSTN Advisory 606) | You cannot manually edit outward tax in GSTR-3B – fix errors via GSTR-1A before filing, not inside 3B. |
| ITC (Table 4A) auto-populates from GSTR-2B/IMS | Live – Table 4 is auto-populated from GSTR-2B (GSTN advisory on auto-population of GSTR-3B), and GSTR-2B reflects your IMS accept/reject/pending actions since IMS went live in October 2024 | The figure you see is 2B-driven, but you can still edit it manually today – which is exactly why silent over-claims still happen. |
| Manual override of Table 4A removed (full hard-lock) | Widely reported as targeted for the July 2026 tax period onward; no dated GSTN advisory confirming go-live traced as of 25 Sep 2026 | Reconcile every month as if it is already locked – by the time it is confirmed, your process should already be compliant, not scrambling. |
We track this specifically because several aggregator articles state the Table 4A lock as an already-completed fact. Verify current status on the GST portal before relying on it for a filing position, and ask us if you want it confirmed for your GSTIN.
The nine checks before you claim
- Valid documentation – a proper tax invoice or debit note exists for every credit, in the supplier's name and GSTIN correctly stated.
- Reflected in GSTR-2B and actioned in IMS – accept, reject or keep the invoice pending in the Invoice Management System before the 2B refresh on the 14th; an invoice left un-actioned is treated as accepted by default, which is a real trap for disputed invoices.
- Goods or services actually received – no credit on invoices for supplies not yet delivered or performed, even if the invoice already sits in 2B.
- Not blocked under Section 17(5) – exclude motor vehicles, food and beverages, club memberships and similar items unless a specific exception applies.
- Supplier has actually filed and paid – Rule 37A – an invoice in your 2B is not final proof of eligibility; if the supplier has not filed their GSTR-3B for that period, the credit is provisional and reversible on a fixed timeline (see worked example 2).
- 180-day payment test – reverse ITC with interest where the supplier remains unpaid beyond 180 days from the invoice date; re-avail once payment is made in full.
- Proportionate reversal – apply Rule 42 for inputs/input services and Rule 43 for capital goods wherever there is exempt or personal use.
- Reverse charge handled separately – pay RCM liability in cash first (Table 3.1(d)), then claim the corresponding credit; do not let RCM entries hide inside the 2B-based reconciliation.
- Within the Section 16(4) time limit – claim by 30 November of the following financial year, or the GSTR-9 filing date if earlier; there is no condonation once this closes.
Worked example 1: the 180-day reversal and re-claim
A Thane-based trading firm claims ITC of ₹1,80,000 on a purchase invoice dated 10 October 2025 (tax + value ₹11,80,000). Payment to the supplier is still pending on 15 May 2026 – that is 217 days, past the 180-day limit that fell on 8 April 2026. The firm must reverse ₹1,80,000 in the GSTR-3B for the period in which the limit lapsed, along with interest under Section 50 for the period the credit was wrongly retained. Once the firm pays the supplier in full – say, on 20 June 2026 – it can re-avail the same ₹1,80,000 in that month's GSTR-3B; only the interest cost is a real, non-recoverable loss.
Worked example 2: Rule 37A in practice
A services firm avails ITC of ₹3,20,000 across FY 2025-26 on invoices from a vendor who later stops filing returns. As of 30 September 2026, the vendor has still not filed GSTR-3B for the relevant periods. Under Rule 37A, the firm must reverse the full ₹3,20,000 on or before 30 November 2026 – the 30 November deadline is measured from the financial year in which the credit was originally availed (FY 2025-26), not from the invoice date. If the vendor files and pays in, say, February 2027, the firm can re-avail the ₹3,20,000 in the GSTR-3B for that later month, with no further approval needed – but if the firm misses the 30 November reversal deadline, interest runs from the original date of availment.
A practical monthly calendar, not a filing-week scramble
| By when | Action |
|---|---|
| 11th | Confirm key vendors have filed GSTR-1 for the month; follow up on chronic non-filers immediately. |
| 13th–14th | Clear the IMS queue – accept, reject or pend every pending invoice before the 2B refresh. |
| 15th–16th | Match GSTR-2B against the purchase register; flag amount/GSTIN mismatches and missing invoices. |
| Before filing | Check for any 180-day-lapsed invoices and any supplier flagged for Rule 37A exposure this cycle. |
| By 20th | File GSTR-3B on reconciled figures – not on whatever the portal happens to auto-populate. |
If your books are on Zoho Books, much of this calendar can run inside the software: its GSTR-2B reconciliation matches portal data against recorded bills each month, which is how we run it for clients. See our Zoho Books setup and migration service and our IMS and ITC reconciliation SOP service.
Common mistakes we still see
- Claiming ITC the moment an invoice appears in 2B, without checking whether the supplier's own GSTR-3B for that period is actually filed.
- Leaving IMS invoices un-actioned and assuming "no action" is neutral – it defaults to acceptance.
- Treating the 180-day rule as a formality rather than tracking it invoice-by-invoice against an ageing report.
- Missing the Section 16(4) cut-off because annual-return-linked ITC claims were left for the last week of November.
Frequently asked questions
What are the conditions to claim input tax credit under Section 16?
You need a valid tax invoice or debit note, the goods or services must actually be received, the supplier must have reported the invoice so it reflects in your GSTR-2B, the supplier’s tax must actually reach the exchequer (via their GSTR-3B), and you must pay the supplier within 180 days of the invoice date. Miss any one and the credit is at risk of reversal with interest.
Has GSTR-3B ITC editing actually been hard-locked already?
Partly. Table 3.1/3.2 outward liability has been locked and auto-populated from GSTR-1/1A since July 2025, and ITC in Table 4 is auto-populated from GSTR-2B, which in turn reflects your IMS actions. A further step – removing your ability to manually override that auto-populated ITC figure – has been widely reported as targeted around the July 2026 tax period, but we could not trace a dated GSTN advisory confirming it is live as of 25 September 2026. Treat your monthly IMS action and 2B reconciliation as if the lock is already in force; that is the safe working assumption either way.
What is blocked credit under Section 17(5)?
Certain credits are blocked outright – motor vehicles (with limited exceptions), food and beverages, outdoor catering, club memberships, works contract services for immovable property, and goods or services used for personal consumption. Claiming these by mistake means reversal with interest, and repeated occurrences invite closer scrutiny.
What is the 180-day payment rule and how is the reversal calculated?
If you do not pay the supplier (invoice value plus tax) within 180 days of the invoice date, the ITC already claimed must be added back in GSTR-3B along with interest under Section 50, calculated from the date of availment to the date of reversal. Once you pay the supplier in full, even after the 180 days, you can re-avail the same credit – there is no permanent loss, only a cash-flow and interest cost.
What is Rule 37A and when does it force a reversal?
Rule 37A applies when your supplier’s invoice appears in your GSTR-2B but the supplier has not filed their own GSTR-3B for that period. If the supplier still has not filed by 30 September following the end of the financial year in which you availed the credit, you must reverse that ITC in GSTR-3B on or before 30 November of the same following financial year, with interest if reversed late. You can re-avail it the moment the supplier files and pays.
What are Rule 42 and 43 reversals?
Where inputs, input services or capital goods are used partly for taxable supplies and partly for exempt supplies or personal purposes, a proportionate reversal is required under Rule 42 (inputs/input services) and Rule 43 (capital goods), computed on the exempt-turnover ratio and typically trued up annually by September of the following year.
How is ITC on reverse charge (RCM) supplies handled?
RCM liability must first be discharged in cash through Table 3.1(d) of GSTR-3B – it cannot be set off against existing ITC. Once paid, the corresponding credit becomes available, subject to the usual eligibility conditions, and should be reconciled separately from the 2B-based ITC flow since RCM does not route through IMS the same way.
When does the right to claim ITC for a year lapse?
Under Section 16(4), ITC for invoices or debit notes of a financial year must be claimed in a return filed on or before 30 November of the following financial year, or the date of filing the annual return (GSTR-9) for that year, whichever is earlier. There is no extension route once this window closes – the credit lapses permanently.
What is the single most effective habit to avoid ITC trouble?
Move reconciliation from filing week to the middle of the month: match GSTR-2B against your purchase register by the 15th, action every IMS entry (accept, reject or keep pending) before the 2B refresh on the 14th, and chase suppliers who have not filed – rather than discovering the gap only when GSTR-3B is due.
We reconcile your GSTR-2B and purchase register monthly, manage the IMS queue, track 180-day and Rule 37A exposure, and file clean, defensible GSTR-3B returns.
GST Compliance ServicesGST Notice HandlingTalk to CA Somesh Chandak & Associates – we keep your GST input tax credit clean and defensible.
WhatsAppLinkedInSchedule a callDisclaimer: This article is for general guidance only and is not a substitute for advice on your specific facts and the latest law. The Table 4A hard-lock timeline reflects our review of public reporting as of 25 September 2026 and should be verified on the GST portal before you rely on it. Please consult before filing.