GSTR-3B ITC Auto-Population Phase 2: Table 4A Locked, July 2026

What is Phase 2 of GSTR-3B hard locking? From July 2026, the GST portal auto-populates Table 4A of GSTR-3B using data from GSTR-2B and locks the fields so no manual B2B ITC entry is possible. This is the second half of a two-phase reform: Phase 1 (April 2026) locked outward supply reporting, and Phase 2 locks input tax credit, creating a fully system-controlled return.

If you went through the disruption of Phase 1 in April 2026, where the portal rejected any GSTR-3B with a Table 3.1 mismatch, Phase 2 is the mirror image on the ITC side. The difference: Phase 1 stopped you from under-reporting sales. Phase 2 stops you from over-reporting purchases. Together, they make GSTR-3B a near-fully auto-generated return, with only a handful of manual fields left.

For businesses that were already reconciling monthly, this changes little. For those still typing ITC figures manually based on purchase registers, July 2026 is a forced migration. If your books and the portal disagree, the portal wins.

Looking for expert help with GSTR-3B ITC auto-population Phase 2 July 2026 Table 4A locked? The team at Tax Garden, based in Kondapur, Hyderabad, helps Indian SMEs stay compliant end-to-end: filings, notices, and advisory, all in one place.

What Exactly Changed in July 2026

Phase 1 Recap (April 2026)

Table 3.1 of GSTR-3B (outward supplies, tax payable) was auto-populated from GSTR-1 data and made non-editable. If your GSTR-1 showed Rs 10 lakh in taxable supplies, Table 3.1 showed Rs 10 lakh and you could not change it. Any error required amending GSTR-1 first.

Phase 2 (July 2026): The ITC Side

Table 4A(1) of GSTR-3B, which reports ITC on B2B supplies including imports of goods, is now auto-populated from GSTR-2B and hard-locked. The figure that appears in Table 4A(1) is the sum of all ITC marked as "ITC Available" in your GSTR-2B for that period. You cannot type a different number.

The system flow is:

1. Your supplier files GSTR-1 (or uses the Invoice Furnishing Facility for QRMP filers)
2. The invoice appears in your IMS dashboard
3. You accept, reject, or take no action (no action = auto-accept) before the 14th
4. GSTR-2B is generated on the 14th, reflecting accepted invoices as "ITC Available"
5. GSTR-3B Table 4A(1) is auto-populated from GSTR-2B — non-editable
6. You file GSTR-3B by the 20th

The loop is now closed. What your supplier reports determines what you can claim. What you accept in IMS determines what GSTR-2B shows. What GSTR-2B shows determines what GSTR-3B allows. No manual override is possible for B2B ITC.

Which Fields Are Locked and Which Stay Editable

Understanding the exact boundary of the lock is critical. Not everything in Table 4 is auto-populated.

The lock applies specifically to B2B ITC in 4A(1) and ISD credit in 4A(4). Everything else requires your input because the portal has no source data for those fields.

IMS Is Now the Compliance Control Point

Before Phase 2, IMS was a convenience tool. You could use it to manage invoices, or you could ignore it and type your ITC directly. That option is gone.

How IMS Works After Phase 2

Every invoice your supplier files in GSTR-1 appears in your IMS dashboard. You have three options for each invoice:

Accept: The invoice flows into GSTR-2B as "ITC Available" and auto-populates Table 4A(1). You must accept invoices that are genuine and that you intend to claim credit on.

Reject: The invoice is excluded from GSTR-2B. Use this for invoices that are duplicates, relate to someone else, or are fraudulent. Rejection does not affect the supplier's GSTR-1 or their tax liability.

No action: The system treats this as acceptance when GSTR-2B is generated on the 14th. This is the default behaviour and the biggest operational risk. If a supplier files a bogus invoice in your name and you do not notice it in IMS before the 14th, the ITC auto-populates into your return.

The 14th Is Your New Deadline

Before Phase 2, the critical date was the 20th (GSTR-3B filing). Now the critical date is the 14th (GSTR-2B generation). By the 14th, you must have:

1. Reviewed every invoice in IMS
2. Rejected anything incorrect
3. Accepted everything you want to claim
4. Followed up with suppliers whose invoices are missing

After the 14th, your Table 4A(1) figure is set. You cannot change it without amending a prior return.

What Happens When ITC Is Missing

The most common complaint since Phase 2 went live is "my ITC is less than what I purchased." This happens because of supplier-side failures. The ITC is not lost permanently, but it is delayed.

Supplier Has Not Filed GSTR-1

If your supplier has not filed their GSTR-1 for the period, none of their invoices appear in your IMS or GSTR-2B. Your Table 4A(1) will not include this ITC.

Remedy: Contact the supplier and request them to file. Once they file, the invoices will appear in your next month's GSTR-2B. You can claim the ITC in a subsequent month. Under Section 16(4), you have until the 30th of November of the following financial year (or the date of filing the annual return, whichever is earlier) to claim ITC for any invoice.

Invoice Amount Mismatch

If the supplier filed the invoice in GSTR-1 but with a different amount than your purchase register, the ITC in GSTR-2B will reflect the supplier's amount, not yours.

Remedy: Coordinate with the supplier to file an amendment in the next GSTR-1. Alternatively, if the supplier's amount is lower than yours, you can only claim the lower amount. If the supplier's amount is higher, you are under no obligation to claim the excess, but it will auto-populate unless you reject the difference.

Credit Note Not Processed

If a supplier has issued a credit note but not reported it in GSTR-1, your GSTR-2B will still show the original invoice ITC. This creates a risk of over-claiming, which the department will flag during assessment.

Remedy: Track credit notes separately. If a credit note is pending in the supplier's GSTR-1, consider reducing your ITC claim through Table 4B (reversal) to avoid mismatch.

Impact on Different Business Types

Regular Monthly Filers

Monthly filers are the most affected. Every month, the cycle repeats: IMS review by the 14th, GSTR-2B on the 14th, GSTR-3B by the 20th. The window between GSTR-2B generation and GSTR-3B filing is six days. Any discrepancy discovered after the 14th cannot be corrected in that period's return.

QRMP Filers

Quarterly filers under the QRMP scheme get a quarterly GSTR-2B. The same Phase 2 lock applies: Table 4A(1) is auto-populated from the quarterly GSTR-2B. The difference is timing: QRMP filers have a wider window to manage IMS because GSTR-2B is generated once a quarter, not monthly. However, IMS invoices accumulate for three months, making the review task larger.

Exporters and SEZ Units

Exporters claiming refunds on zero-rated supplies must ensure their input ITC in GSTR-3B matches GSTR-2B exactly. Any manual inflation of ITC to increase the refund claim is now impossible. The refund application (RFD-01) cross-references GSTR-3B Table 4A, and since that table is now system-controlled, the maximum refund is capped at what GSTR-2B shows.

Composition Scheme Taxpayers

Composition scheme taxpayers do not file GSTR-3B. They file CMP-08 quarterly. Phase 2 does not apply to them because composition dealers cannot claim ITC in the first place.

The Monthly Compliance Calendar After Phase 2

The post-Phase 2 GST calendar requires a tighter monthly rhythm. Here is the revised sequence:

The 14th is the pivot. Everything before it is preparation; everything after it is computation and filing. If you miss the 14th with unreviewed invoices, your GSTR-3B will either include ITC you should not claim (risk of DRC notice) or exclude ITC you should claim (cash flow loss).

Reconciliation Is No Longer Optional

Before Phase 2, you could reconcile GSTR-2B against your purchase register as a best practice. After Phase 2, reconciliation is mandatory by design. If your books say you have Rs 5 lakh in ITC but GSTR-2B shows Rs 4.5 lakh, your GSTR-3B will carry Rs 4.5 lakh. The Rs 50,000 gap is not a rounding error you can fix later; it is blocked until the source data (supplier's GSTR-1) catches up.

A Practical Reconciliation Workflow

1. On the 14th: Download GSTR-2B from the GST portal in JSON or Excel format
2. Match against purchase register: Compare invoice-by-invoice. Flag invoices in your books that are missing from GSTR-2B (supplier not filed) and invoices in GSTR-2B not in your books (potential fraud or misposted supplier)
3. Quantify the gap: Separate the gap into (a) supplier-side filing delays (will self-correct) and (b) genuine errors (require amendment or reversal)
4. For supplier delays: Send formal communication to the supplier requesting GSTR-1 filing. Maintain a supplier compliance tracker
5. For errors: If the supplier filed a wrong amount, request an amendment. If a bogus invoice appeared, reject it in IMS (for the next period) and reverse any ITC already claimed
6. Document everything: GSTR-3B is now an auditable, system-generated document. Your reconciliation workpaper is the only evidence that you reviewed the auto-populated figures

Common Mistakes in the First Month

Based on the first month of Phase 2 (July 2026 returns filed in August 2026), practitioners are reporting these recurring errors:

Not reviewing IMS at all. Some businesses assumed IMS was optional. When they opened GSTR-3B, Table 4A showed a figure they did not recognise. By then, GSTR-2B was already generated and the figure was locked.

Rejecting invoices that should have been accepted. Hasty IMS review led some businesses to reject genuine invoices. Once rejected, the ITC does not appear in GSTR-2B. The invoice will reappear in the next month's IMS, but the ITC is delayed by a full period.

Ignoring credit notes. The auto-populated figure includes the net effect of invoices and credit notes in GSTR-2B. Businesses that tracked only invoices and not credit notes found their Table 4A lower than expected.

Filing GSTR-3B without computing Table 4B. Table 4B (reversals) is still manual. Businesses that filed without computing Rule 42/43 proportional credit or Section 17(5) blocked credit will face assessment notices later. The portal does not validate Table 4B against any system data.

How This Connects to the Broader GST Reform

Phase 2 is not an isolated change. It is part of a stated GSTN roadmap to make GSTR-3B a fully auto-generated return:

• 2024–25: IMS launched, auto-population introduced as editable
• April 2026: Phase 1 locks Table 3.1 (outward supplies) — see our Phase 1 guide
• July 2026: Phase 2 locks Table 4A (B2B ITC)
• Future phases: Table 4B (reversals) may be auto-computed using Rule 42/43 data from the return itself

The end state is a return where the taxpayer verifies and files rather than fills and files. Until Table 4B is also automated, GSTR-3B remains partially manual, but the system-controlled portion now covers the two largest figures: output tax and input tax.

What Should Your CA or Accounts Team Do Right Now

If you have not already adjusted your GST monthly close for Phase 2, act on these items before the next return cycle:

1. Assign a daily IMS reviewer. Someone must log into the GST portal and review new invoices in IMS every working day, not once a month. Flag anything suspicious immediately.

2. Set a hard internal deadline of the 12th. GSTR-2B is generated on the 14th. Your IMS review must be complete by the 12th to allow a two-day buffer for follow-ups.

3. Build a supplier compliance tracker. Track which suppliers file GSTR-1 on time and which do not. For habitual late filers, consider re-negotiating payment terms to include a clause linking payment to timely GSTR-1 filing.

4. Reconcile on the 14th, not the 20th. The GSTR-2B download on the 14th is your reconciliation source. Run the match immediately. Do not wait until the 18th.

5. Keep Table 4B computation rigorous. The temptation to focus only on the locked fields and rush through the manual ones will increase. Table 4B reversals under Section 17(5) and Rules 42 and 43 are still manual and still auditable. Get them right.

6. Consider managed GST compliance. If your team does not have the bandwidth to run daily IMS checks and monthly GSTR-2B reconciliation, outsource to a compliance partner that does this systematically.

Phase 2 and the AATO Amendment Window

July 2026 also brings the AATO (Aggregate Annual Turnover) amendment window for FY 2025-26. GSTN's revised advisory allows taxpayers to amend their AATO on the portal between 1 July and 31 July 2026. Tax officers will review the amended figures from 1 August to 15 August 2026. If your AATO was incorrectly computed (due to wrong classification of exempt supplies, inter-state vs intra-state errors, or missed turnover), amend it during this window. AATO affects your eligibility for QRMP scheme, composition scheme, and e-invoice thresholds.

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This guide is based on the Finance Ministry's November 2025 confirmation of the Phase 2 timeline, GSTN portal-level implementation effective July 2026 return period, and practitioner reports from the first filing cycle. For the legal framework underpinning the hard-lock mechanism, refer to Rule 88D of the CGST Rules, 2017. For the Phase 1 (outward supply) hard-lock details, see our April 2026 action plan. Tax Garden recommends consulting a qualified GST practitioner for business-specific ITC reconciliation.