Understanding GST in India: Constitutional Framework, Dual Model, and Tax Structure

Taxation forms the financial backbone of public administration, funding critical infrastructure such as national transportation networks, healthcare systems, education, and social security programs. In India, fiscal powers have historically been divided between the Union Government and the State Legislatures. However, prior to 2017, this division produced a heavily fragmented, highly complex indirect tax ecosystem characterized by multiple overlapping levies, cascading tax burdens, and interstate trade barriers.

On July 1, 2017, the Government of India implemented the Goods and Services Tax (GST), ushering in the most significant indirect tax reform in modern Indian economic history. Under the governing motto “One Nation, One Tax”, GST dismantled dozens of legacy state and central levies to create a unified national market.

This guide provides a rigorous architectural breakdown of the Indian GST system: the economic defects that made reform essential, the constitutional foundation established by the 101st Constitutional Amendment Act, the operational mechanics of the Dual GST model, and the critical distinction between taxes subsumed into GST and those that remain outside its scope.

1. Direct vs. Indirect Taxation: The Foundational Divide

To understand the mechanics of GST, one must first recognize where it sits within public finance theory: the boundary between direct and indirect taxes.

flowchart TD
    Tax["Public Revenue: Tax System"]
    Tax --> DT["Direct Tax"]
    Tax --> IT["Indirect Tax"]

    DT --> DT_Desc["Levied directly on income or profits<br/>• Non-shiftable tax burden<br/>• Progressive structure<br/>• Examples: Income Tax, Corporate Tax"]
    IT --> IT_Desc["Levied on supply of goods and services<br/>• Intermediary collects from end consumer<br/>• Burden shifted to ultimate buyer<br/>• Examples: GST, Customs Duty"]

Direct Taxes

A direct tax is assessed and collected directly from the individual or corporate entity that generates the taxable income or wealth. There are no intermediaries between the taxpayer and the sovereign treasury:

Non-Shiftability: The statutory liability and financial incidence rest on the exact same legal entity. An individual cannot legally shift their personal income tax burden to another citizen.
Primary Examples: Personal Income Tax under the Income-tax Act, 1961, and Corporate Tax assessed on the net profits of corporate enterprises.

Indirect Taxes

An indirect tax is imposed on economic transactions—specifically the manufacture, sale, transport, or consumption of goods and services.

Tax Shifting: While registered suppliers or merchants legally remit the tax to the government, they act as collection intermediaries, passing the economic burden forward across the supply chain until it reaches the final retail consumer.
Economic Characteristics: Indirect taxes promote social welfare by funding sovereign infrastructure, but because they are built into retail pricing, they can exert an inflationary influence on everyday goods if not balanced by input tax offsets.
Primary Examples: The Goods and Services Tax (GST) and Customs Duty on cross-border international commerce.

2. Why Reform Was Urgent: Structural Defects of the Pre-GST Regime

Before July 2017, Indian indirect taxation suffered from structural inefficiencies that burdened domestic commerce and discouraged cross-border investment:

Multiplicity of Levies: A standard manufacturing business was subjected to Central Excise Duty upon manufacturing, Central Sales Tax (CST) or State Value Added Tax (VAT) upon sale, Entry Tax or Octroi at municipal borders, and Service Tax on professional inputs.
The “Tax-on-Tax” Cascading Effect: Under the fragmented framework, central taxes could not generally offset state taxes. For example, when a manufacturer paid Central Excise Duty on factory output, the State Government calculated State VAT on the gross invoice value inclusive of the excise duty. Taxpayers were routinely forced to pay tax on top of previously assessed tax.
Interstate Commercial Friction: Crossing state borders required tedious border checkposts, waybills, and physical transit clearances. Central Sales Tax (CST) was an origin-based levy that could not be claimed as an input tax credit by buyers in destination states, incentivizing companies to maintain inefficient, state-specific warehouses merely to avoid CST liabilities.
Administrative and Compliance Inflation: Businesses were forced to register under multiple independent tax departments, maintain disparate accounting books, undergo separate audits, and litigate conflicting classifications across dozens of state jurisdictions.

3. The Constitutional Foundation: 101st Amendment Act, 2016

Under the Constitution of India, the Union Parliament and State Legislatures operate under demarcated legislative domains defined in Schedule VII (Union List, State List, and Concurrent List). Historically, Parliament held exclusive power to tax services and manufacturing (Excise), while States held exclusive power to tax intra-state sales of goods (Sales Tax / VAT). Neither sovereign body had the constitutional authority to levy a single unified tax on the simultaneous supply of both goods and services across the entire nation.

To resolve this constitutional obstacle, Parliament passed the Constitution (122nd Amendment) Bill, 2014, which received Presidential assent on September 8, 2016, and was officially enacted as the Constitution (101st Amendment) Act, 2016.

Landmark Constitutional Provisions

Article 246A (Concurrent Powers & The Dual Control Model): This landmark article conferred concurrent legislative authority upon both Parliament and every State Legislature to enact laws governing goods and services tax. This enabled the simultaneous exercise of taxing authority without either level of government subordinating its constitutional sovereignty.
Article 269A (Inter-State Commerce and Imports): Mandates that GST on inter-state supplies of goods and services, as well as cross-border imports, shall be levied and collected exclusively by the Government of India, with revenues apportioned between the Union and the States according to formulas determined by Parliament upon the recommendation of the GST Council.
Article 366(12A) (Statutory Definition of GST): Formally defines Goods and Services Tax as “any tax on supply of goods, or services or both, except taxes on the supply of the alcoholic liquor for human consumption.”

Following the constitutional amendment, four central bills were passed by Parliament and became Acts on April 12, 2017:

The Central Goods and Services Tax (CGST) Act, 2017
The Integrated Goods and Services Tax (IGST) Act, 2017
The Union Territory Goods and Services Tax (UTGST) Act, 2017
The Goods and Services Tax (Compensation to States) Act, 2017

Complementary State GST (SGST) Acts were sequentially passed by every State Legislature, paving the way for the nationwide launch on July 1, 2017.

4. The Dual GST Model Explained

India adopted a Dual GST Model, reflecting its federal constitutional framework. In this model, tax is levied concurrently by both the Central Government and the respective State Government on a single commercial transaction.

flowchart TD
    Supply["Commercial Supply"]
    Supply --> Intra["Intra-State Supply<br/>(Supplier & Place of Supply in Same State)"]
    Supply --> Inter["Inter-State Supply or Import<br/>(Supplier & Place of Supply in Different States)"]

    Intra --> CGST["CGST (Central GST)<br/>Remitted to Central Treasury"]
    Intra --> SGST["SGST / UTGST<br/>Remitted to State or UT Treasury"]
    
    Inter --> IGST["IGST (Integrated GST)<br/>Collected by Centre & Apportioned to Destination State"]

The Four Pillars of the Tax Structure

Tax Component	Meaning	Statutory Jurisdiction	Destination Principle
CGST	Central Goods and Services Tax	Levied on intra-state supplies; administered by the Central Government.	Retained by the Centre.
SGST	State Goods and Services Tax	Levied on intra-state supplies; administered by the respective State Government.	Retained by the originating State.
UTGST	Union Territory Goods and Services Tax	Levied on intra-territorial supplies within Union Territories lacking a legislative assembly (e.g., Ladakh, Andaman & Nicobar).	Retained by the Union Territory Administration.
IGST	Integrated Goods and Services Tax	Levied on inter-state commerce, cross-border imports, and supplies to SEZs; administered by the Centre.	Apportioned equally between the Centre and the destination State.

Intra-State vs. Inter-State Transactions in Practice

Intra-State Supply Example: A furniture manufacturer in Pune, Maharashtra sells office desks to an IT firm in Mumbai, Maharashtra for ₹100,000. Assuming an applicable GST rate of 18%:
- CGST (9%): ₹9,000 is credited to the Central Government.
- SGST (9%): ₹9,000 is credited to the Maharashtra State Government.
- Total Invoice Tax: ₹18,000.
Inter-State Supply Example: The same Pune manufacturer sells office desks to a client in Bengaluru, Karnataka for ₹100,000.
- IGST (18%): ₹18,000 is levied under the IGST Act. The Central Government collects the full amount and routes the state share to Karnataka (the destination state where consumption occurs).
Cross-Border Imports: Under Article 269A, goods imported into India are deemed inter-state supplies. They attract Basic Customs Duty (BCD) plus IGST (which replaced the earlier Countervailing Duty [CVD] and Special Additional Duty [SAD]). For imported services, IGST alone applies.

5. Scope of Subsumption: What Is Inside and Outside GST?

GST was not built simply by adding another tax; it was created by repealing and subsuming seventeen major central and state levies into a consolidated credit chain.

Central Taxes Subsumed into CGST / IGST

Central Excise Duty
Duties of Excise (Medicinal and Toilet Preparations)
Additional Duties of Excise (Goods of Special Importance and Textiles)
Countervailing Duty (CVD) and Special Additional Duty (SAD)
Service Tax
Central Surcharges and Cesses relating to supply of goods and services

State Taxes Subsumed into SGST

State Value Added Tax (VAT) / Sales Tax
Central Sales Tax (CST)
Luxury Tax
Entry Tax (all forms) and Octroi
Entertainment and Amusement Tax (except when levied by local municipal bodies)
Taxes on Advertisements
Taxes on lotteries, betting, and gambling
State Surcharges and Cesses

graph LR
    subgraph Subsumed_Central["Subsumed Central Levies"]
        CE["Central Excise"]
        ST["Service Tax"]
        CVD["CVD & SAD"]
    end

    subgraph Subsumed_State["Subsumed State Levies"]
        VAT["State VAT"]
        CST["Central Sales Tax"]
        ET["Entry Tax & Luxury Tax"]
    end

    subgraph Unified_GST["The Unified GST Regime"]
        CGST["CGST"]
        SGST["SGST"]
        IGST["IGST"]
    end

    Subsumed_Central --> CGST
    Subsumed_Central --> IGST
    Subsumed_State --> SGST
    Subsumed_State --> IGST

Taxes Not Subsumed (Remaining Independent)

Certain levies remain outside the GST architecture and continue to be governed by their respective statutory enactments:

Customs Duty: Basic Customs Duty (BCD), Anti-Dumping Duty, and Safeguard Duty continue under the Customs Act, 1962.
State Property Taxes & Stamp Duties: Stamp Duty and Registration Fees on real estate transfers remain under exclusive state jurisdiction.
Electricity Duty: Levied by states on the consumption and sale of electricity.
Local Taxes: Taxes levied by local authorities, Panchayats, or Municipalities (such as local entertainment taxes and toll taxes).
Road & Passenger Tax: Motor vehicle registration and transit taxes administered by state transport departments.

Explicitly Excluded Commodities

Under constitutional and statutory provisions, specific goods are excluded from the current scope of GST:

Alcoholic Liquor for Human Consumption: Constitutionally carved out under Article 366(12A). States retain exclusive constitutional power to levy State Excise Duty on manufacture and State VAT on sale.
The “Five Petroleum Products”: Under Section 9(2) of the CGST Act, GST will apply to these commodities only from a future date recommended by the GST Council. In the interim, they remain subject to Central Excise Duty and State VAT:
- Petroleum Crude
- High-Speed Diesel (HSD)
- Motor Spirit (commonly known as Petrol)
- Natural Gas
- Aviation Turbine Fuel (ATF)
Tobacco and Tobacco Products: While tobacco is subject to GST, the Central Government uniquely retains the concurrent power to levy Central Excise Duty on its manufacture alongside GST compensation cesses.

6. Key Takeaways & Architectural Summary

Destination-Based Consumption Tax: GST is levied at the point of consumption rather than the point of origin. Tax revenue flows to the state where goods or services are consumed, eliminating the distortive effects of origin-based levies like CST.
Dual Control Sovereignty: Article 246A empowers Parliament and State Legislatures concurrently. Intra-state sales split revenue equally between CGST and SGST/UTGST; inter-state sales attract IGST administered by the Centre and shared with destination states.
Cascading Elimination: By absorbing 17 central and state taxes into a single credit continuum, businesses can claim input tax credits on virtually all operational purchases, preventing double taxation.
Constitutional Exceptions: Alcoholic liquor is constitutionally excluded from GST, while five petroleum products remain under legacy excise and VAT regimes until the GST Council resolves to bring them into the GST net.

7. Frequently Asked Questions (FAQ)

What is the primary difference between CGST, SGST, and IGST?

CGST and SGST are applied concurrently to intra-state sales (where the supplier and the place of supply are located within the same state); CGST revenue goes to the Union and SGST to the State. IGST applies to inter-state sales (across different states) and international imports, collected centrally and divided between the Centre and the consuming state.

Why was a constitutional amendment required to introduce GST in India?

Under the original 1950 Constitution, legislative taxing powers were strictly separated: the Centre could tax manufacturing and services, while States had exclusive jurisdiction over the sale of goods. Neither government could tax the unified supply of both. The 101st Constitutional Amendment Act (Article 246A) created concurrent legislative power for both jurisdictions.

Why is alcohol for human consumption not taxed under GST?

Alcohol for human consumption is explicitly excluded by the constitutional definition of GST in Article 366(12A). Bringing alcohol under GST would require a fresh constitutional amendment. Individual states continue to collect State Excise Duty and State VAT on alcoholic beverages.

How are cross-border imports handled under GST?

Under Article 269A, imports of goods or services are legally deemed inter-state supplies. For goods, IGST is assessed alongside Basic Customs Duty at the port of entry. For services imported from foreign entities, IGST is paid by the domestic recipient under the Reverse Charge Mechanism (RCM).