Tamil Nadu's GST Collection Paradox: Falling Domestic Collections, Rising State Receipts

What the April-September 2026 data really tells us - and what it does not

Tamil Nadu's GST numbers for the first half of FY 2026-27 present an apparent contradiction.

During April to September 2026, the State reported domestic gross GST collections of Rs 63,962 crore, reflecting a year-on-year decline of 3.2%. More significantly, five consecutive months from May to September recorded collections below their corresponding 2025 levels. Yet, during substantially the same period, Tamil Nadu's post-settlement SGST increased by 16.13% to Rs 44,266 crore.

How can GST collections decline while the State's reported SGST receipts increase?

The answer lies partly in understanding what the different GST collection measures represent. Domestic gross GST, pre-settlement SGST and post-settlement SGST are related measures, but they are not interchangeable. The distinction assumes particular importance in a destination-based tax such as GST, where IGST settlement and utilisation of cross-tax credits can materially affect the amount ultimately transferred to a State.

The data therefore establishes a collection concern deserving investigation. It does not, by itself, establish declining economic activity, tax evasion, industrial migration or a deterioration in Tamil Nadu's final GST receipts.

Five consecutive months of contraction cannot be ignored

The domestic collection trend is undoubtedly the starting point.

Tamil Nadu recorded Rs 13,561 crore in April 2026, representing growth of 4.3%. Thereafter, the trajectory changed. Five successive months from May to September registered year-on-year contraction. Cumulatively, the half-year ended September 2026 at Rs 63,962 crore, 3.2% below the corresponding period.

May is particularly important. Collections declined from Rs 11,582 crore in May 2025 to Rs 9,834 crore in May 2026 - a shortfall of Rs 1,748 crore. Across May to September, the aggregate shortfall was Rs 2,679 crore. May alone accounts for approximately 65.25% of that shortfall.

That concentration has an important administrative implication. Before attributing Tamil Nadu's collection decline to a broad deterioration in compliance or economic activity, the first exercise should be to identify whether a relatively small number of large taxpayers, sectors, exceptional payments or timing differences explain the May movement.

At the same time, May cannot explain the entire phenomenon. Even excluding May, June to September collections were Rs 40,567 crore against Rs 41,498 crore in the corresponding previous-year period - a decline of approximately 2.24%. There is therefore an underlying weakness beyond the exceptional May decline.

The comparison with other major States makes the question sharper

Tamil Nadu's performance also differs materially from several comparable major States. For April-September 2026, the supplied data reports domestic GST growth of 8.6% for Maharashtra, 11.1% for Karnataka, 11.9% for Gujarat, 10.1% for Haryana, 14.2% for Uttar Pradesh, 13.8% for Telangana and 10.3% for Kerala. All-India domestic collections grew by approximately 6.1%, while Tamil Nadu contracted by 3.2%.

The divergence is significant, but caution is necessary. A GST collection league table cannot establish that one State's economy is performing better than another's. States differ in manufacturing and services composition, exports, interstate trade, applicable rate mix, ITC intensity and concentration of large taxpayers.

Equally, the comparison cannot simply be ignored. Tamil Nadu's domestic collection growth is approximately 9.3 percentage points below the national domestic growth rate, which strengthens the case for a State-specific diagnostic exercise.

More GST registrations, but lower collections

The registration data introduces another dimension. Tamil Nadu's reported GSTIN stock increased from 12,43,141 at the end of April to 12,81,780 at the end of September 2026 - an increase of 38,639 GSTINs, or approximately 3.11%. Thus, the decline in collections cannot be explained by a shrinking reported registration stock.

But neither should the increase of 38,639 be described automatically as '38,639 new taxpayers'. A GSTIN stock may include multiple registrations of the same business, newly registered entities that have not completed a full return cycle, nil filers, composition taxpayers and registrations with varying levels of taxable activity.

The more meaningful question is whether Tamil Nadu's effective tax-paying base is growing at the same pace as its reported registration base. Answering that requires segregation of active filers, nil filers, non-filers, cash-paying taxpayers, turnover bands and newly registered cohorts.

The real paradox: pre-settlement SGST fell, but post-settlement SGST rose

The most important part of the analysis emerges when the SGST figures are decomposed.

Pre-settlement SGST declined by Rs 515 crore. However, the implied settlement component increased by approximately Rs 6,662 crore. Consequently, post-settlement SGST increased by approximately Rs 6,147 crore.

In other words, the improvement in the reported State receipt measure was driven principally by the settlement component. This should neither be dismissed nor mis-characterised. It is not evidence of an exceptional discretionary transfer to Tamil Nadu. IGST settlement is inherent in the architecture of GST. Sections 17 and 18 of the IGST Act govern, inter alia, apportionment and settlement and transfers associated with utilisation of credits.

Accordingly, weaker locally attributed collections can coexist with stronger State receipts under a destination-based GST. However, the calculated settlement residual alone does not tell us how much represents recurring settlement, earlier-period adjustments or other settlement categories. Detailed settlement statements would be necessary before concluding that the 48.43% increase represents a recurring trend.

Has GST rate rationalisation affected Tamil Nadu disproportionately?

There is another issue that deserves considerably more attention. The GST rate rationalisation measures implemented from September 2025 mean that the effective rate structure applicable during parts of the comparative periods may differ.

Consider the automobile-components sector. Under the GST 2.0 rate rationalisation, automobile parts that were earlier subject to GST at 28% have been brought under a uniform GST rate of 18%, irrespective of their HS classification.

To illustrate the impact, assume the taxable value of automobile parts increases from Rs. 100 to Rs. 110, reflecting a 10% increase in turnover. At the earlier rate of 28%, GST on Rs. 100 would be Rs. 28. At the revised rate of 18%, GST on Rs. 110 would be only Rs. 19.80. Thus, notwithstanding a 10% increase in the underlying taxable value, the GST yield would decline from Rs. 28 to Rs. 19.80 - a reduction of approximately 29.29%.

This demonstrates why a decline in GST collections after rate rationalisation cannot, by itself, be treated as evidence of declining business activity. In States such as Tamil Nadu, with a significant automobile and auto-component manufacturing base, the sectoral impact of such rate reductions requires to be separately quantified before conclusions are drawn from headline GST collection figures. This is merely illustrative, but it demonstrates why a decline in GST collection cannot automatically be equated with declining sales or economic contraction.

The more difficult question is whether Tamil Nadu's industrial and consumption composition has made it more exposed to particular rate reductions than States such as Maharashtra, Gujarat or Karnataka. That proposition cannot presently be established from aggregate collection data. It requires an HSN/SAC-wise analysis comparing taxable values, applicable rates, sectoral weights and ITC restrictions before and after rationalisation.

ITC utilisation may also change the collection picture

GST liability does not necessarily translate into an equivalent cash payment. Eligible input tax credit may be utilised against output tax subject to the statutory framework. Consequently, taxable turnover may remain stable - or even increase - while the composition of tax discharge changes between cash and credit.

The research data itself does not establish whether this has occurred in Tamil Nadu. However, a change in utilisation of IGST credit against SGST could potentially be relevant when examining the combination of weaker pre-settlement SGST and stronger settlement receipts.

A proper analysis should therefore reconcile, taxpayer-wise: output tax liability, ITC utilised, cash discharged, IGST credit utilisation and settlement consequence. Merely comparing cash collection figures cannot answer this question.

Refund growth should not be blamed without evidence

Refunds represent another area in which conclusions must be carefully framed. National domestic GST refunds increased by approximately 21.4% during the half-year. However, the reports do not disclose corresponding Tamil Nadu specific refund amounts or the number of refund claims. Consequently, it would be unsupported to conclude that higher refunds caused Tamil Nadu's collection decline.

There is an additional conceptual issue. In the reporting framework examined, refunds are deducted after gross revenue is reported. Higher refunds therefore do not mechanically cause a fall in the gross domestic collection series.

More importantly, a legally admissible refund is a statutory entitlement. Revenue analysis should distinguish between detecting an incorrect refund and delaying a valid refund merely because aggregate collections are under pressure.

Aggregate revenue weakness cannot become evidence against individual taxpayers

A State-wide collection shortfall may legitimately trigger analytical scrutiny. It cannot, however, become a substitute for evidence in proceedings against individual taxpayers.

If the data ultimately identifies compliance concerns, proceedings must still satisfy the applicable statutory requirements concerning the proper officer, jurisdiction, limitation, relied-upon material, opportunity of hearing and a reasoned adjudication. Aggregate revenue targets cannot establish suppression of turnover, wrongful availment of ITC or tax evasion by a particular registered person.

Revenue analytics should therefore operate as a risk-identification mechanism, not as a presumption of liability.

What should Tamil Nadu examine next?

Instead of beginning with a broad enforcement response, the appropriate exercise would be a structured reconciliation of the State's GST data.

The first layer should identify the GSTINs contributing most significantly to the absolute year-on-year decline, particularly in May. The analysis should then determine whether those movements arose from continuing business activity, one-time payments in the previous year, timing differences, cancellations, changes in jurisdiction or genuine turnover contraction.

The second layer should construct an HSN/SAC and sector-wise bridge to measure the effect of rate changes. The third should reconcile output liability against cash and ITC discharge. The fourth should examine interstate supplies, zero-rated turnover and export concentration. The fifth should reconcile the approximately Rs 20,419 crore implied settlement component against the actual settlement schedules.

Finally, Tamil Nadu-specific refund data should be examined by claim category, underlying tax period, sanction, adjustment and actual disbursement date. Only after completing these reconciliations should the residual unexplained decline be treated as a potential compliance or enforcement concern.

Conclusion: Concern is justified; conclusions must wait

Tamil Nadu's GST performance during April-September 2026 raises a legitimate question. A 3.2% contraction in domestic GST collections, five successive months of negative year-on-year growth and substantial underperformance relative to national domestic growth and several major States cannot simply be dismissed.

At the same time, the other half of the picture is equally important. Reported post-settlement SGST increased by 16.13% to Rs 44,266 crore, with the increase being principally explained by a substantially larger settlement component. The registered GSTIN stock also continued to expand.

On the presently available evidence, therefore, it would be premature to describe Tamil Nadu's position as a GST revenue crisis. Equally, the strength of post-settlement receipts should not become a reason to disregard persistent weakness in the domestic collection series.

The real question is not simply: 'Why has Tamil Nadu's GST collection fallen?' It is more precisely: 'After neutralising rate changes, settlement effects, ITC utilisation, refunds, timing differences and exceptional taxpayer movements, how much of Tamil Nadu's domestic GST decline remains unexplained?'

That residual number would provide a far stronger foundation for tax policy and administration than the headline collection percentage alone. GST revenue statistics must first be reconciled before they are interpreted - and interpreted before they are enforced.

Note: This analysis is based on GST collection data reported in the six monthly GSTN reports covering the period from April to September 2026. The figures are provisional and should be read subject to the data limitations, reconciliation differences and other qualifications identified in the underlying report.

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By Adv. Ganesh Prabhu