New GST ITC Set-Off Rules 2026: Priority Order, IGST First Rule & GSTR-3B Examples

TL;DR Summary:

1. The mandatory IGST-first rule remains unchanged: exhaust all IGST credit before touching CGST or SGST credit — this has been in force since February 2019 under Section 49A and Rule 88A. 2. CGST and SGST can never be cross-utilized against each other under any circumstance; surplus CGST or SGST credit can only go toward residual IGST liability, never toward the other’s head. 3. From February 2026, GSTN Advisory 647 gives taxpayers a new choice: once IGST ITC is fully exhausted, you can apply CGST and SGST credits against residual IGST liability in any sequence you prefer — CGST first, SGST first, or any split. 4. From January 2026, the interest calculation in Table 5.1 of GSTR-3B now factors in the minimum cash balance held in the Electronic Cash Ledger from the due date, reducing interest on the amount already funded — and this system-computed interest figure is locked and cannot be edited downward. 5. Late reporting of past-period invoices in GSTR-1 now automatically triggers period-specific interest through the new Tax Liability Breakup Table — catching errors before filing is more critical than ever. 6. The wrong set-off already filed must be corrected via Table 4 amendment in the subsequent month’s GSTR-3B; it cannot be undone in the same return.

The GST ITC set-off order requires IGST credit to be used first against IGST liability, then surplus IGST can offset CGST and SGST; CGST credit applies to CGST first and SGST credit to SGST first, with any surplus from either going toward residual IGST liability. CGST and SGST can never be cross-utilised against each other under any circumstance. From February 2026, GSTN Advisory 647 added one new flexibility: once IGST ITC is fully exhausted, taxpayers can choose to apply CGST and SGST credits against residual IGST liability in any sequence they prefer, along with a revised interest formula that now accounts for the minimum cash balance held in the Electronic Cash Ledger from the due date of filing.

Confused about which credit to use first — IGST, CGST, or SGST? If you have been guessing your way through the Input Tax Credit set-off process in GSTR-3B, you are not alone.

 The rules around ITC utilisation have been a source of genuine confusion for businesses since GST came into force — and January 2026 brought the most significant update to the GSTR-3B filing mechanism in years.

On 30 January 2026, GSTN issued Advisory No. 647 announcing key enhancements in interest calculation, tax liability breakup, and IGST credit utilisation in GSTR-3B. This guide explains what changed, what stayed the same, and how to apply the correct set-off sequence in your monthly filing.

Why the Old Set-Off Rules Caused Confusion

When GST was introduced in 2017, the original Section 49 of the CGST Act prescribed a utilisation sequence but the GST portal did not always enforce it automatically. Businesses filed GSTR-3B with incorrect set-off sequences and discovered errors only during assessments or audits.

Two specific problems persisted for years. First, interest computation on the portal was not aligned with the legal proviso of Rule 88B(1) — which says interest is payable only on net cash liability. The portal often computed interest on a higher base, ignoring cash already sitting in the Electronic Cash Ledger. Second, once IGST ITC was exhausted, the portal did not give taxpayers flexibility in choosing whether to apply CGST or SGST credit against residual IGST liability. Both problems were addressed by GSTN Advisory 647 in January 2026.

The 2019 Notification That Set the Foundation

Before understanding the 2026 changes, it helps to understand the foundation they rest on. The Central Goods and Services Tax (Amendment) Act, 2018, effective from 1 February 2019, inserted Sections 49A and 49B into the CGST Act and established the mandatory IGST-first rule that continues to govern ITC utilisation today.

Foundational Notifications (2019 Framework)

Notification No. 02/2019 – Central Tax, dated 29 January 2019

→ Brought Sections 49A and 49B into force with effect from 1 February 2019.

Notification No. 16/2019 – Central Tax, dated 29 March 2019

→ Inserted Rule 88A in the CGST Rules, 2017. Effective from 1 April 2019.

Circular No. 98/17/2019-GST, dated 23 April 2019

→ CBIC clarification resolving ambiguities in Rule 88A’s language on cross-utilisation order.

Section 49A made it mandatory to exhaust IGST credit fully before any CGST or SGST credit can be touched. Section 49B empowered the Government to prescribe the order of utilisation by notification. Rule 88A operationalised this — and Circular 98/17/2019 clarified that after IGST credit is exhausted, any residual IGST credit can be applied to CGST and SGST liability in any order at the taxpayer’s discretion.

This 2019 framework remained the operative law through December 2025. The CGST and SGST cross-utilisation prohibition — that CGST credit can never offset SGST liability and vice versa — has been in force since Day 1 of GST and has not changed.

GSTN Advisory 647 (January 2026): What the Official  Notification Says

Change 1 — Updated Interest Computation Formula (Table 5.1)

The advisory states: ‘From January-2026 tax period onwards, the interest calculation in table 5.1 of GSTR-3B on portal has been enhanced, providing the benefit of the minimum cash balance available in the Electronic Cash Ledger of the taxpayer from the due date of return filing until the date of tax payment (offset) in line with the proviso to Rule 88B(1) of the CGST Rules, 2017.’

The official revised interest computation formula as specified in Advisory 647:

Interest = (Net Tax Liability – Minimum Cash Balance in ECL from due date to date of debit) × (No. of days delayed / 365) × Applicable Interest Rate

The ‘minimum cash balance’ means the lowest balance available in the Electronic Cash Ledger during the delay period — from the due date of GSTR-3B until the date of actual payment. Even if additional cash is deposited later, the benefit applies only to the extent of the balance maintained from the due date itself.

Therefore:

·         If sufficient balance was maintained continuously from the due date, that balance gets reduced from the net cash liability for interest computation.

·         If the balance dropped at any time during the period, the benefit is restricted to that lower amount.

This change finally aligns the portal’s computation with the legal proviso of Rule 88B(1) read with Section 50 of the CGST Act, 2017, which has always provided that interest should be charged only on net cash liability.

Change 2 — System-Computed Interest in Table 5.1 is Now Locked–    

   (Critical Filing Impact — Downward Edit Blocked)

The advisory further states: ‘The interest auto-populated on the basis of the revised computational formula mentioned above, in table 5.1 of GSTR-3B shall be non-editable and taxpayers would not be allowed to amend the auto-populated values downward. It may be noted that the interest auto-populated in GSTR-3B is only the minimum interest that is required to be paid by the taxpayer. However, the taxpayers needed to self-assess their correct interest liability, and amend the auto populated values upward, if required.’

Change 3 — Auto-Population of Tax Liability Breakup Table

The advisory states: ‘The tax liability breakup table in GSTR-3B captures the supplies of previous tax periods, reported in current period. The tax is being paid for such supplies in current tax period. Hence, for the filing of GSTR-3B from January-2026 tax period onwards, the GST Portal shall auto-populate the Tax Liability Breakup Table in GSTR-3B on the basis of date of documents related to supplies reported in GSTR-1 / GSTR-1A / IFF pertaining to any previous tax period, where the corresponding tax liability has been discharged in the current period’s GSTR-3B.’

Key features as stated in the advisory:

• Auto-populated values are suggestive in nature

• Taxpayers may modify these values upward based on their own records and computations, if required

• Navigation: Login → GSTR-3B Dashboard → Table 6.1 (Payment of Tax) → Tax Liability Breakup

Late Invoice Reporting Now Triggers Interest Automatically

• If past-period invoices are reported in the current month’s GSTR-1, the portal can now map the liability to the earlier period and compute period-specific interest — even if the current GSTR-3B is filed on time.

• Late GSTR-1 reporting now carries an automatic and irreversible interest risk that did not exist before January 2026

Change 4 — Update in Table 6.1: Suggestive Cross-Utilisation of ITC (IGST Flexibility)

The advisory states: ‘From January-2026 period onwards, once the available IGST ITC has been fully exhausted, the GST Portal will allow to pay IGST liability in Table 6.1 of GSTR-3B using available CGST and SGST ITC in any sequence.’

This is the change most relevant to the GST ITC set off order 2026 discussion. Before January 2026, the portal’s sequence for applying CGST and SGST credits against a residual IGST liability was either rigid or ambiguous. Advisory 647 formally enables taxpayers to choose the sequence — CGST first, SGST first, or a combination — once IGST ITC is fully used up.

Implementation Timeline — Advisory 647 + Update 649

January 2026 tax period:  Interest formula update (Change 1), Table 5.1 lock (Change 2), and Tax Liability Breakup auto-population (Change 3) all apply.

February 2026 tax period onwards:  GSTN Update 649 (dated 19 February 2026) clarified that the IGST utilisation flexibility in Table 6.1 (Change 4) is operational from February 2026 only — not January 2026.

Taxpayers filing GSTR-3B for January 2026 should not expect the IGST utilisation flexibility to be available for that period.

Change 5 — Collection of Interest via GSTR-10 for Cancelled Taxpayers

The advisory clarifies the procedure for recovery of interest in cases where a taxpayer’s GST registration has been cancelled. Earlier, there was uncertainty regarding the calculation and recovery of interest under Section 50 where the last applicable GSTR-3B was filed after the due date, particularly because the GSTIN had already been cancelled.

The advisory now clarifies that:

• interest on delayed filing of the last applicable GSTR-3B will be automatically computed; and
• such interest will be recovered through GSTR-10.

This clarification provides greater certainty in the compliance process for cancelled taxpayers and helps reduce disputes relating to interest computation and recovery.

New Priority Order: Full ITC Set-Off Sequence (2026)

Incorporating the 2019 foundation and the February 2026 change, the complete GST ITC set off order 2026 is as follows. The IGST-first rule under Section 49A and Rule 88A remains fully intact. What changed in 2026 is only the flexibility at Step 5 and 6 below.

Step	ITC Used	Applied Against	Basis / Notes
1	IGST Credit	IGST Liability	Mandatory first — Section 49A, Rule 88A
2	IGST Credit (balance)	CGST Liability	After IGST liability is nil — taxpayer’s choice of order
3	IGST Credit (balance)	SGST Liability	After IGST liability is nil — taxpayer’s choice of order
4	CGST Credit	CGST Liability first	Intra-head priority — Section 49(5)(b)
5	CGST Credit (surplus)	IGST Liability	After IGST ITC exhausted — any sequence per Advisory 647 (Feb 2026)
6	SGST Credit	SGST Liability first	Intra-head priority — Section 49(5)(c)
7	SGST Credit (surplus)	IGST Liability	After IGST ITC exhausted — any sequence per Advisory 647 (Feb 2026)
8	CGST Credit	SGST Liability	NOT PERMITTED — absolute prohibition
9	SGST Credit	CGST Liability	NOT PERMITTED — absolute prohibition

The key principle: Use IGST credit first against IGST, then CGST, then SGST. Then CGST against CGST and SGST against SGST only. From February 2026, once IGST ITC is zero, CGST and SGST credits can discharge residual IGST liability in any sequence the taxpayer chooses. CGST and SGST cannot be cross-utilised against each other under any circumstance.

Step-by-Step Worked Examples with GSTR-3B

Example A: New IGST Flexibility (February 2026 onwards — IGST ITC Nil)

Tax Head	ITC Available	Output Liability
IGST	Nil	₹50,000
CGST	₹50,000	Nil
SGST	₹50,000	Nil

Before February 2026: The portal sequence for applying CGST/SGST to IGST liability was ambiguous or rigid, potentially forcing an unwanted split.

From February 2026 (Advisory 647): The taxpayer can choose to use 100% CGST credit (₹50,000) to discharge the entire IGST liability — preserving the full SGST credit balance for future periods. Or the reverse. Or any proportion. The choice is entirely the taxpayer’s once IGST ITC is confirmed at zero.

Example B: Interest Saving Under the New Formula (January 2026 onwards)

Particulars	Before January 2026	From January 2026
Net GST liability	₹1,00,000	₹1,00,000
Cash in ECL on due date	Not consistently factored	₹40,000 (minimum balance)
Delay	20 days	20 days
Interest computed on	Often ₹1,00,000	₹60,000 (₹1,00,000 – ₹40,000)
Interest rate	18% per annum	18% per annum
Approx. interest payable	₹986.3	₹591.8
Saving	—	₹394.5 (on ₹40,000 ECL balance)

What Happens If You Apply the Wrong Set-Off Order?

Applying an incorrect ITC utilisation order in GSTR-3B is treated as an incorrect return with the following consequences:

•         Interest at 18% per annum on any resulting short payment of tax — now computed automatically by the portal with downward edit blocked

•         Scrutiny notices under Section 61 of the CGST Act triggered by mismatched ITC utilisation patterns

•         Denial of credit and recovery proceedings in cases involving erroneous refund claims

•         Penalty exposure under Section 122 for intentional or repeated non-compliance

Wrong set-off in GSTR-3B must be corrected via amendment in the subsequent month’s return. The amendment is made in Table 4 of the next GSTR-3B. Given that system interest is now locked downward from January 2026, catching errors before filing is more important than ever.

Common Errors and How to Correct Them

Error 1: Paying Cash Without Checking IGST Credit Balance

Problem: Taxpayers pay CGST or SGST in cash even when IGST credit is available in the Electronic Credit Ledger.

Fix: Always verify the IGST credit balance on the GST portal before filing. Apply IGST credit first against IGST liability, redirect any surplus to CGST or SGST. Never go to cash before IGST credit is zero.

Error 2: Attempting CGST-SGST Cross-Utilisation

Problem: Surplus CGST credit is redirected to pay SGST liability (or vice versa) to avoid cash outflow.

Fix: This is not permissible under any circumstance. If CGST credit is in surplus and SGST liability is unpaid, the SGST must be paid in cash. Surplus CGST carries forward.

Error 3: Not Planning Cash in ECL Before the Due Date

Problem: Cash is deposited into ECL after the due date of GSTR-3B, meaning the minimum ECL balance during the delay period is zero — and the new interest formula provides no relief.

Fix: Fund the ECL at least partially before the due date. Even partial funding reduces the interest base under the new formula. Late deposits after the due date do not reduce interest for the period before they were deposited.

Error 4: Late GSTR-1 Reporting of Past-Period Invoices

Problem: Invoices from a previous period are reported in the current month’s GSTR-1. Under the new Tax Liability Breakup Table, the portal maps the liability to the earlier period and computes interest for that period automatically.

Fix: File GSTR-1 on time every month. Where backdated invoices must be reported, self-assess the resulting interest liability and amend Table 5.1 of GSTR-3B upward accordingly.

Error 5: Wrong Set-Off Already Filed

Problem: GSTR-3B has already been filed with an incorrect ITC utilisation order.

Fix: Wrong set-off in GSTR-3B must be corrected via amendment in the subsequent month’s GSTR-3B using Table 4 adjustments. Consult a GST professional to determine whether the amendment triggers additional interest liability under the new locked-interest regime.

How PKC Can Help

The January and February 2026 changes to GSTR-3B are not merely portal updates — they represent a structural shift in compliance. Interest is now computed automatically and locked. Tax liability is mapped period-wise. ITC utilisation flexibility is expanded but comes with more responsibility to plan correctly before filing.

At PKC Management Consulting, our GST compliance team works with businesses across industries to ensure that ITC utilisation is handled correctly every month, GSTR-3B is filed without error, and any amendments are addressed before they escalate into notices or assessments.

Our GST services include:

·         Monthly GSTR-3B preparation and filing with correct ITC set-off sequencing under the 2026 rules

·         Electronic Cash Ledger planning to minimise interest exposure under the new formula

·         GSTR-2B reconciliation and ITC mismatch resolution

·         GST return amendment and rectification support

·         GSTR-1 discipline review to prevent Tax Liability Breakup interest triggers

·         GST notice handling and departmental representation

Have questions about your GST ITC set-off, GSTR-3B filings, or the January 2026 advisory changes? Reach out to our team — we are happy to help.

FAQ (Frequently Asked Questions)

Q1: What is the new GST ITC set-off rule in 2026?

GSTN Advisory 647 (30 January 2026) made two changes: it updated the interest calculation formula to factor in minimum ECL cash balance (effective January 2026), and it enabled taxpayers to use CGST and SGST credit in any sequence against residual IGST liability once IGST ITC is exhausted (effective February 2026 per Update 649). The core IGST-first rule under Section 49A and Rule 88A remains unchanged.

Q2: In what order should I utilize my ITC?

Use IGST credit first against IGST, then CGST, then SGST. Then use CGST credit against CGST liability first — any surplus can go to IGST. Use SGST credit against SGST liability first — any surplus can go to IGST. From February 2026, once IGST ITC is fully exhausted, you can apply CGST and SGST credits to residual IGST liability in any sequence you choose. CGST and SGST cannot be cross-utilised against each other under any circumstance.

Q3: Can CGST credit be set off against SGST liability?

No. CGST and SGST credits cannot be cross-utilised. This prohibition is absolute and has not changed with Advisory 647. If CGST credit is surplus and SGST liability is outstanding, the SGST must be paid in cash. The surplus CGST credit carries forward.

Q4: How do I apply ITC set-off in GSTR-3B correctly?

In Table 6.1 of GSTR-3B, apply IGST ITC first against IGST liability. Redirect surplus to CGST then SGST. Apply CGST ITC to CGST liability, then SGST ITC to SGST liability. From February 2026, if IGST ITC is zero and IGST liability remains, you can choose whether to apply CGST or SGST credit (or both in any proportion) to discharge it. Pay any remaining liability from the Electronic Cash Ledger.

Q5: What if I used the wrong ITC set-off order?

Wrong set-off in GSTR-3B must be corrected via amendment in the subsequent month’s return. Given that system interest in Table 5.1 is now locked downward from January 2026, it is critical to identify and correct errors before filing rather than after.

Q6: What is the latest notification on GST ITC rules?

GSTN Advisory No. 647 dated 30 January 2026 is the most recent update, covering interest computation, tax liability breakup, and IGST ITC utilisation flexibility. GSTN Update No. 649 dated 19 February 2026 clarified the implementation timeline — the IGST flexibility applies from February 2026 onwards, not January 2026.

Q7: Can IGST credit be used to pay both CGST and SGST?

Yes. After IGST credit is first applied against the full IGST liability, any remaining IGST credit balance can be used to pay CGST liability and then SGST liability. Per Circular 98/17/2019 and Rule 88A, the taxpayer has discretion over the order of CGST versus SGST when applying surplus IGST credit.