What is GST Number? Format & Decode GSTIN Structure

If you’ve ever received a tax invoice or filed a GST return, you’ve likely come across a 15-digit code called the GST number. It’s more than just a registration ID—it’s the unique tax identity of every GST-registered business in India. Knowing how to decode this number can help you avoid fraud, validate documents, and stay compliant. Whether you’re a small trader or a large company, understanding the GSTIN structure is essential for smooth business operations.

What is a GST Number (GSTIN)?

A GSTIN, or Goods and Services Tax Identification Number, is a unique 15-digit alphanumeric code assigned to every taxpayer registered under the GST regime. It is mandatory for businesses exceeding the prescribed turnover threshold to obtain a GSTIN. This number is used for all GST-related activities, including filing returns, claiming input tax credit, and issuing invoices. The GSTIN replaces previous tax identification numbers, bringing all indirect tax registrations under a single, unified system.

GST Number Format and Structure Explained

The GSTIN is structured as a 15-digit alphanumeric code, where each segment holds specific significance. This structure not only ensures uniqueness but also encodes vital information about the taxpayer, such as their state, PAN, and registration details. Here’s a quick overview of what each part represents:

1–2 digits: State Code

Represents the state or union territory as per the Indian Census 2011. For example, ‘27’ stands for Maharashtra, ‘07’ for Delhi, and ‘29’ for Karnataka.

3–12 digits: PAN of the Business or Entity

These ten characters are the Permanent Account Number (PAN) of the business or individual. PAN is mandatory for GST registration.

13th digit: Entity Code

Indicates the number of registrations a business entity has within a state under the same PAN. For the first registration, it is ‘1’; for the second, ‘2’, and so on. After ‘9’, it continues with the alphabet's ‘A’ to ‘Z’.

14th digit: Default ‘Z’

This digit is kept as ‘Z’ for all regular taxpayers. It is reserved for future use or special categories.

15th digit: Checksum Digit

This is an alphanumeric character used as a checksum for error detection, ensuring the authenticity of the GSTIN.

Example of a GSTIN and Explanation

Let’s take a sample GSTIN: 27ABCDE1234F1Z5

1. 27 – State code for Maharashtra
2. ABCDE1234F – PAN of the business
3. 1 – First registration under this PAN in Maharashtra
4. Z – Default value
5. 5 – Checksum digit

This GSTIN indicates that the business is registered in Maharashtra, with a PAN of ABCDE1234F. It is their first GST registration in the state, and the GSTIN is valid according to the checksum.

Also Read : Benefits of Filing Income Tax Return (ITR) 2025

How to Apply for a GST Number in India

A GST Number or GSTIN (Goods and Services Tax Identification Number) is a unique 15-digit code assigned to every registered taxpayer in India. Understanding its structure helps businesses verify authenticity and ensure compliance.

• First 2 digits: State code (01 for Jammu & Kashmir, 27 for Maharashtra, etc.)
• Next 10 digits: PAN of the taxpayer
• 13th digit: Entity number of the same PAN in a state
• 14th digit: Alphabet “Z” by default
• 15th digit: Checksum digit for validation

How to Verify a GST Number Online?

To ensure authenticity, it’s important to verify GST numbers, especially when dealing with new vendors or partners. You can do this in just a few steps:

1. Visit the official GST Portal:www.gst.gov.in
2. Click on ‘Search Taxpayer’ and select ‘Search by GSTIN/UIN’.
3. Enter the GSTIN and the captcha code, then click ‘Search’.
4. The portal will display the business’s legal name, registration status, and other details if the GSTIN is valid .

If valid, the portal will display details like the business name, registration status, type of taxpayer, and address.

Importance of Understanding GSTIN Structure

The GSTIN is crucial for businesses, consumers, and tax authorities, ensuring transparency, compliance, and legitimacy in India’s GST ecosystem.

Importance for Businesses

1. Validating Suppliers
2. Verifying GSTIN ensures that suppliers are legitimate and registered, preventing fraudulent transactions.
3. Seamless Input Tax Credit (ITC)
4. Correct GSTIN usage enables businesses to claim accurate input tax credits, reducing tax liability.
5. Legal Compliance and Credibility
6. A valid GSTIN establishes business credibility and ensures compliance with invoicing regulations.
7. Interstate Trade Facilitation
8. GSTIN simplifies interstate transactions, allowing smooth movement of goods and services.
9. Expansion Opportunities (E-commerce, Tenders)
10. Registered GSTIN allows businesses to participate in government tenders and e-commerce platforms.
11. Avoiding Penalties
12. Using the correct GSTIN reduces the risk of penalties for non-compliance or incorrect invoicing.

Significance for Consumers

1. Ensuring Legitimacy of Businesses
2. Consumers can verify GSTIN to confirm that the seller is legally registered.
3. Combating Fraud
4. GSTIN verification helps prevent fraudulent transactions and fake invoices.
5. Verifying Invoice Details
6. Consumers can check invoices for accuracy and authenticity, ensuring correct GST charges.

Importance for Tax Authorities

1. Tracking Transactions
2. GSTIN allows authorities to monitor business transactions across states efficiently.
3. Reducing Tax Evasion
4. A unique GSTIN helps curb tax evasion by ensuring proper reporting and accountability.
5. Efficient Administration
6. Tax authorities can streamline compliance checks, audits, and reporting using GSTIN data.

Businesses that wrongly record GSTINs may lose tax credits or attract notices from tax departments.

Also Read: GST Registration Process – How to Apply Online

Who Needs to Obtain a GST Number?

A GST Number (GSTIN) is mandatory for certain businesses based on turnover, nature of activity, or inter-state operations. Even if not required, voluntary registration can offer several benefits. Understanding eligibility helps ensure compliance and access to tax advantages.

1. Turnover-Based Mandatory Registration

Businesses exceeding specified turnover thresholds must register for GST:

• Goods: ₹40 lakh in normal states; ₹20 lakh in special category states
• Services: ₹20 lakh in normal states; ₹10 lakh in special category states

2. Activity-Based Mandatory Registration

Certain business activities require GST registration regardless of turnover:

• Inter-state Suppliers: Businesses supplying goods/services across states
• E-commerce Sellers: Individuals or entities selling via e-commerce platforms
• E-commerce Operators: Platforms facilitating online sales
• Casual Taxable Persons: Those making occasional taxable supplies in India
• Non-Resident Taxable Persons: Foreign businesses supplying goods/services in India
• Agents & Input Service Distributors (ISDs): Entities distributing input tax credits
• Reverse Charge Mechanism: Businesses liable to pay tax under reverse charge

3. Voluntary GST Registration

Even if not mandatory, businesses may register voluntarily to gain advantages:

• Claim input tax credit on purchases
• Conduct inter-state business legally
• Enhance business credibility with clients and banks
• Enable selling on e-commerce platforms

Difference Between GSTIN and GSTN

The Goods and Services Tax Identification Number (GSTIN) and the Goods and Services Tax Network (GSTN) are two key terms frequently used in India’s GST system. While they may sound similar, they serve distinctly different purposes within the tax ecosystem.

Understanding the distinction between GSTIN and GSTN helps businesses navigate GST compliance smoothly and leverage the system effectively.

How to Spot Fake GST Numbers?

Fake GST numbers are commonly used in fraudulent invoices, so verifying them is crucial. Here are key ways to identify fake GSTINs:

1. Check Format: Ensure the GSTIN follows the correct 15-digit structure — state code (2 digits), PAN (10 characters), entity number, default letter ‘Z’, and checksum digit.
2. Verify Online: Use the official GST portal (www.gst.gov.in) or trusted third-party tools to check GSTIN validity and business details.
3. Match Business Information: Confirm that the GSTIN matches the supplier’s name and address as listed on the invoices.
4. Check Registration Status: Ensure the GSTIN is active, not suspended or deregistered.
5. Monitor Filing History: Look for consistent GST return filings by the supplier.

Always report suspicious GSTINs to the GST authorities for action. Verifying GST numbers helps prevent fraud and ensures smooth, compliant business transactions.

Benefits of Having a GST Number

Obtaining a GST Number (GSTIN) is more than just a compliance requirement. It provides financial, operational, and legal advantages that support business growth, transparency, and credibility.

1. Financial & Compliance Benefits

• Access to Input Tax Credit (ITC)
• Businesses can claim credit for taxes paid on purchases, reducing overall tax liability.
• Elimination of Tax-on-Tax Effect
• GST removes cascading taxes, ensuring that goods and services are taxed only once.
• Improved Cash Flow
• Claiming ITC and timely filing helps maintain better cash flow management.
• Simplified Online Procedures
• GST registration allows easy online filing, invoicing, and return submission, reducing paperwork.
• Reduced Compliance Burden
• Unified GST consolidates multiple indirect taxes, simplifying compliance for businesses.
• Higher Registration Threshold
• Businesses with turnover above prescribed limits must register, which formalizes operations and compliance.
• Composition Scheme for Small Businesses
• Eligible small businesses can opt for the composition scheme, paying tax at a lower rate with simplified compliance.

2. Business & Growth Opportunities

• Enhanced Credibility with GSTIN
• A valid GSTIN builds trust among suppliers, customers, and financial institutions.
• Increased Market Reach Across States
• Registered businesses can sell products and services interstate without legal hurdles.
• Access to E-Commerce Platforms
• GST registration enables selling on online marketplaces, expanding customer base.
• Eligibility for Government Tenders
• Businesses with GSTIN are eligible for government contracts and tenders, opening new revenue streams.
• Better Logistics Efficiency
• Formal registration facilitates smoother supply chain and logistics operations across states.

3. Legal & Administrative Benefits

• Regulation of the Unorganized Sector
• GST brings informal businesses into the formal economy, ensuring fair competition.
• Legal Recognition Through GSTIN
• Registration provides official identity and legitimacy for businesses.
• Avoidance of Penalties
• Registered GSTIN ensures compliance with GST laws, reducing the risk of fines.
• Improved Business Transparency
• GSTIN facilitates transparent invoicing and reporting, strengthening business reputation.

Conclusion

Decoding the GSTIN structure empowers businesses and individuals to verify the authenticity of GST numbers, avoid fraud, and ensure proper tax compliance. Always check the GSTIN on the official portal before entering into business transactions or claiming input tax credit. This verification process helps confirm the taxpayer’s legal name, registration status, and business details - essential steps not only for compliance but also when applying for a business loan, where accurate GST data supports loan eligibility. Using the official GST portal or trusted verification tools ensures accuracy and protects your business interests. Staying vigilant with GSTIN validation promotes transparency and smooth compliance in India’s tax ecosystem.

FAQs

Q.1. What does each digit in the GSTIN represent?

A. The first two digits are the state code, the next ten are the PAN, the 13th is the entity number, the 14th is a default ‘Z’, and the 15th is a checksum digit.

Q.2. How can I check if a GST number is valid?

A. Visit the GST portal (www.gst.gov.in), use the ‘Search Taxpayer’ feature, enter the GSTIN, and view the registration details.

Q.3. Is GSTIN the same as a GST registration number?

A. GSTIN is the official registration number assigned to every GST-registered taxpayer.

Q.4. Can a business have more than one GSTIN?

A. A business can have multiple GSTINs if it operates in more than one state or has multiple business verticals in the same state. Each registration will have a unique 13th digit in the GSTIN.

Q.5. Is PAN mandatory for GST registration?

A. Yes, PAN is mandatory for GST registration, except for non-resident taxable persons, who may use a different identification number.

Q.6. What should I do if I find an invalid GSTIN on an invoice?

A. Do not proceed with the transaction. Report the issue to the concerned authorities and verify with the supplier.

Q.7. Can I update or modify details linked to my GST number?

A. Yes. Businesses can update or modify GST registration details like business name, address, email, mobile number, or authorized signatory through the official GST portal. Certain changes may require supporting documents for verification.

Q.8. What happens if I use a wrong GST number on an invoice?

A. Using an incorrect GSTIN can lead to rejection of input tax credit (ITC) claims for the recipient and potential compliance issues for your business. Always verify GSTINs before issuing invoices.

Q.9. Can two businesses operate under the same GST number?

A. No. Each GSTIN is unique to a legal entity and its place of business. Multiple businesses cannot share the same GST number. Separate GST registration is required for each entity.

Q.10. Is GST number mandatory for freelancers or consultants?

A. Freelancers and consultants need GST registration only if their annual turnover exceeds ₹20 lakh (₹10 lakh for special category states) or if they provide services to clients in other states. Otherwise, registration is voluntary.

Q.11. How can I find the GST number of a company or supplier?

A. You can verify a GSTIN on the official GST portal using the company name or GST number. This ensures authenticity before claiming input tax credit or making transactions.

Q.12. What are the consequences of not having a GST number?

A. Without GST registration, a business cannot legally charge GST, claim input tax credit, sell interstate, or participate in government tenders. Non-compliance may lead to penalties and legal complications.

Q.13. How do I cancel my GST number if my business shuts down?

A. A GSTIN can be cancelled through the GST portal by submitting an application with reasons for closure and relevant supporting documents. Authorities will verify before processing cancellation.

Q.14. Can a GST number be reactivated after cancellation?

A. Yes. Cancelled GST registrations can be reactivated by applying through the GST portal, subject to verification by tax authorities.

Q.15. How long does it take to get a GST number after application?

A. Typically, GST registration is approved within 7–10 working days if all documents are correct. Delays may occur if additional verification is required.

Q.16. Is a GST number mandatory for exporting goods or services?

A. Yes. Exporters must have a GST registration to claim

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