GST Number — What It Is, How to Get It, and Why Your Business Needs One
A GST number is not merely an administrative requirement — it is the tax identity of a business under India's Goods and Services Tax framework. Formally called a GSTIN (Goods and Services Tax Identification Number), this 15-digit code is used in every tax transaction a registered business conducts. Whether your business is issuing invoices, claiming input tax credit, or filing returns, the GST number is central to all of it. This page explains what the Number means, how it is structured, who needs one, and how to obtain it.
Understanding What a GST Number Actually Is
A GST number is a unique alphanumeric identifier issued by the tax authority to every person or entity registered under the Goods and Services Tax Act. It serves as proof of GST registration and is required on every tax invoice issued by a registered taxpayer. The number is state-specific — a business with operations in multiple states receives a separate GST Number for each state of operation.
The broader context of obtaining a GST Number starts with the GST registration process, which determines eligibility, required documents, and the application procedure.
The Structure of a GST Number Decoded
Each GST Number follows a fixed 15-character format:
| Position | Characters | Meaning |
|---|---|---|
| 1–2 | Digits | State code (e.g., 27 for Maharashtra, 29 for Karnataka) |
| 3–12 | Alphanumeric | PAN of the registered entity |
| 13 | Digit | Entity count within the state under the same PAN |
| 14 | Letter | Default 'Z' |
| 15 | Alphanumeric | Check digit for error detection |
Understanding the structure also helps when looking up how to get your GSTIN — the PAN connection means any business applying for a GST Number must first have a valid PAN.
Who Must Obtain a GST Number
Mandatory GST registration — and consequently a GST Number — is required for:
- Businesses whose annual turnover exceeds ₹40 lakh (goods) or ₹20 lakh (services) in most states
- Businesses operating in special category states with lower thresholds
- All interstate suppliers regardless of turnover
- E-commerce sellers and operators
- Casual and non-resident taxable persons
- Businesses paying tax under the reverse charge mechanism
Voluntary registration is also available for businesses below the threshold who wish to access input tax credit or enhance their commercial standing.
How to Apply for a GST Number
The application for a GST Number is filed on the GST Common Portal. The process involves submitting business information, promoter details, address proof, PAN-linked documents, and bank account information. The detailed, field-by-field process is covered in the online application steps guide.
After submission, an Application Reference Number (ARN) is generated. The tax officer reviews the application and — if complete — issues the GST Number and registration certificate within approximately 7 working days. Understanding what it costs to register for GST helps applicants plan before they begin. For businesses applying from cities like GST registration in Hyderabad or GST registration in Pune, local applicability rules remain the same as the national framework.
Verifying a GST Number
Once a GST number is obtained, it can be verified through the GST portal's "Search Taxpayer" feature. Verification is useful for businesses receiving invoices from vendors — confirming that a supplier's GST Number is valid and active before accepting a tax invoice protects the buyer's eligibility to claim input tax credit. If the GSTIN entered on an invoice does not match the portal record, the invoice may be invalid for ITC purposes.
What Changes After Your Business Gets a GST Number
Once a GST Number is issued, the registered business takes on specific compliance obligations: filing periodic returns, issuing tax invoices in the prescribed format, maintaining GST-compliant accounts, and depositing collected tax. If any registered details — such as the business address or authorised signatory — change, the GST amendment process must be followed to update them formally. Should the business cease operations or no longer require GST registration, a cancellation procedure applies, and in certain cases, GST revocation may be needed if the Number was cancelled by the authority.
Businesses that do not have a physical office address and need to obtain a GST Number can use a virtual office as a registered business address, which is accepted by the GST authority for registration purposes.
Why IndiaFilings for Your GST Number
IndiaFilings assists businesses across India in obtaining their GST numbers accurately and without unnecessary delays. From reviewing PAN details and preparing address proof to completing the portal application and managing officer queries, the team handles every aspect of the process. For businesses navigating GST compliance for the first time, having professional support from the application stage reduces errors and ensures that the GST Number is obtained in the shortest possible time.
Get your GST Number with professional assistance — start the process with IndiaFilings today.
